Wilhelmus
Yes. You're using the correct Holistic not Self-Centric viewpoint. (my Ref[25]).
Apparently Western Europeans and US Students are the worst at this!! Asked 'Where is the truck?" The self centric response may be "around 300m away, behind me, to the South, moving away." The proper (Holistic) view would be; "On the road beside the red building moving south." This is the 'Lab Frame' error. Lodge made it (1893 Fig 13) and we've kept on repeating it. There is only ONE VALID FRAME for measurement, the SAME frame as the object.
The first respondent may have been on any of 10 moving buses, so the answer tells us nothing of the truck. SR assumes that doesn't matter, to explain constant light speed. Now that is otherwise explained (by the c/n of plasma- ion gas/shocks) we need to recognise it DOES matter, and all paradoxes and anomalies evaporate!
However! This shows your logic below fails. Remember Einstein said "Space without Ether is unthinkable" (Leiden 1921). There may indeed be a continuum reference frame, (CMBR) except it's a DIScontinuum, precisely as Einstein predicted;
(Gothenburg 1923); "There are then an infinite number of inertial frames which are in uniform translational motion relative to each other, and hence there is also an infinite number of mutually equivalent, physically preferred states of motion. Time is absolute, i.e.independent of the choice of the particular inertial frame; it is defined by more characteristics than logically necessary, although - as implied by mechanics - this should not lead to contradictions with experience. Note in passing that the logical weakness of this exposition from the point of view of the stipulation of meaning is the lack of an experimental criterion for whether a material point is force free or not; therefore the concept of the inertial frame remains rather problematical."
All the DFM has now done is solved that problem. If only AE has space travel to hep he'd have done it himself.
Peter