You wrote: " 'Sub specie aeterni Poincaré, in my opinion, is correct. . . .' Really? I beg to differ'.
Are you differing with Poincare or Einstein?
What does "Sub specie aeterni" mean in the context Einstein used it? I think it means 'superficially'.
I quote an extract from your reference (3): http://www.zionism-israel.com/Albert_Einstein/albert_einstein_Geometry_Experience.htm
"Envisaged in this way, axiomatic geometry and the part of natural law which has been given a conventional status APPEAR as epistemologically equivalent".
"Sub specie aeterni Poincaré, in my opinion, is right. The idea of the measuring-rod and the idea of the clock co-ordinated with it in the theory of relativity do not find their exact correspondence in the real world. It is also clear that the solid body and the clock do not in the conceptual edifice of physics play the part of irreducible elements, but that of composite structures, which may not play any independent part in theoretical physics. But it is my conviction that in the present stage of development of theoretical physics these ideas must still be employed as independent ideas; for we are still far from possessing such certain knowledge of theoretical principles as to be able to give exact theoretical constructions of solid bodies and clocks.".
"Envisaged in Poincare's way G + P convention APPEAR to give equivalent theories. If you take this superficially Poincare is right".
This is why I say that Einstein was not agreeing with G+P = N. If you scroll down a few paragraphs, you find Einstein stating HIS POSITION.
"The question whether the structure of this continuum is Euclidean, or in accordance with Riemann's general scheme, or otherwise, is, according to the view which is here being advocated, properly speaking a physical question which must be answered by experience, AND NOT A QUESTION OF A MERE CONVENTION TO BE SELECTED ON PRACTICAL GROUNDS. Riemann's geometry will be the right thing if the laws of disposition of practically-rigid bodies are transformable into those of the bodies of Euclid's geometry with an exactitude which increases in proportion as the dimensions of the part of space-time under consideration are diminished".
So Einstein's view was not G+P = N. His view was more like G_P = N
History repeats itself. Newton made it clear in the Preface to the very first edition of Principia, that he is writing a provisional make shift theory because he is unable with the present knowledge to develop the "Truer Method of Philosophy" (i.e. Geometric_physics based on least particles - read as quanta of energy). But his followers took hold of the makeshift theory, turn it into a dogma and formed an orthodoxy hostile to any new thinking. Same thing has happened with Einstein.
I quote an extract from my essay:
Einstein wrote: ".. But quite apart from the superiority of one or the other (i.e., NM or RT), the fictitious character of fundamental principles is perfectly evident from the fact that we can point to two essentially different principles, both of which correspond with experience to a large extent.". (1, p.393). It must be clear from this statement that Einstein held that not only Newtonian foundation to be fictitious, but also that the foundation of his own theory of relativity to be fictitious!!.
In regard to the fictitious axioms in the foundations of physics Einstein wrote: "If, then, it is true that the axiomatic basis of theoretical physics cannot be extracted from experience but must be freely invented (fictitiously), can we ever hope to find the right way? Nay more has the right way any existence outside our illusions? ......". We need to note that in answering the above question , Einstein firmly asserted that the right way will be based on simplest of mathematical ideas: " ..without a hesitation that there is, in my opinion a right way, and that we are capable of finding it (in the future) ...Our experience hitherto justifies us in believing that nature is a realization of the simplest conceivable mathematical ideas. (thus quite in contrast to the abstruse mathematical formalisms of SRT and GRT), I am convinced that we can (i.e. WILL be able to) discover by means of purely mathematical constructions, the concepts and laws connecting them with phenomena" (1, p. 398). We must note that Einstein indicates here candidly that RT is directing not quite towards the 'right way' and implies that RT will be surpassed and replaced when the 'right way' is found.
In regard to Geomeric_physics We must remember Galileo: "Philosophy (i.e. Physics) is written in this grand book, the universe, which stands continually open to our gaze. But the book cannot be understood unless one first learns to comprehend the language and read the letters in which it is composed. It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures without which it is humanly impossible to understand a single word of it; without these, one wanders about in a dark labyrinth" .
I have developed the type of geometric_physics, Newton and Einstein were predicting. It is only a small beginning. Summary of it is compiled for the FQXi essay.
I developed "Geometrodynamics of energy" having identified the following foundational problems and to rectify them.
I quote the list of problems:
"We may note that among the problematic foundational concepts created by Newton that have congenitally infected RT and QM are a) the primacy of the concepts of space and time, b) representation of bodies as mass-points without internal structure, c) consideration of centrifugal force as a pseudo-force, d) the closed system with the consequent inability to account for inflow and outflow of energy between the system and the field etc. e) Not recognizing that it is by the two quantities of energy (Mc2 and pc) fusing together to form a system that motion occurs. f) the omission of the fact that a fraction of the applied energy of motion pc gets usurped for the co-movement with the location. g) Not developing the theory with state changes of energy as the basis of its physical geometry. With these congenital foundational problems being inherent in these two progeny theories as well, it should be obvious that revamping of physics must begin from where the problems originated".
If you can find the time, I request you to please have a look at my essay - "A Treatise on Fundamental Problems of Physics" posted on Sep 06 on FQXi. And comment on it.