Stefan,
It seems you may have just slipped back into to the usual 'mode 1' thinking of the first part of my essay rather than rationalise what I wrote. That's not surprising. It IS tricky to get your mind round it and hold it there, so lets take it in stages; (It's worth doing, unless you can't accept there may be ANY alternative to 'backward causality'!)
Let's simplify to one state and start with mirrors, parts of the system not properly addressed and accounted for in any of the experimental analysis! I'm not sure if you know this or not (if not just check) but reflection INVERTS the photon state (equivalent to electron spin flip). So for the same path length; if two parts from a splitter are brought back together and one has had one more reflection, there WILL be destructive interference. This is what we find. All OK so far?
Now if the pair have the SAME number of reflections and the same path length (remember the delays from transmissions through glass, giving a slight 'phase slip, have to be adjusted for) then the OPPOSITE will found! You should see the fully consistent logic in that, Yes?
Now apply that to the experimental set ups and you'll see that assuming it's a 'which path' question is a misunderstanding leading to the confusion so only an illogical analysis is possible.
So called 'Parametric down-conversion' (a fancy name distracting from the fact it 'splits' photons, which is still assumed by most as impossible) is not a 'unique' case but de-rigeur in Huygens construction (recall my redshift video). That means some state and energy is ALWAYS taking both 'paths'. If you've now looked at Harris's (IBM Q cutting edge) video you'll see the confirmation that some of these assumptions from even 15 years ago are false. (and please, there's no need for insulting suggestions I 'don't understand' experiments I've studied dozens of over decades, and even done some.)
Now just take the Classical Hypothesis and carefully 'run through' each experiment step by step. You'll find IT DOES PRECISELY PREDICT ALL the findings! (including those 'once removed' by the statistical analysis). If there's anything specific you get stuck on or think it can't resolve, just ask!
A few others are now getting their heads round the classical derivation, which really is quite an intellectual test, including to overcome the cognitive dissonance you're struggling with (see below, and Bill McHarris essay) so I hope you can stay focused and get back the grasp of it you seemed to have earlier.
Best
Peter