Counterpoint, 65% is big enough and I don't have to move my hands off the home position just to get to the Function F1-F12 keys while still having dedicated arrows (in fact, 60% is big enough for most people, but standalone arrows seems to be a desirable feature). I also disagree with the bit about finger gymnastics, if the keys are all within reach of your fingers while your hands are positioned on the home row, why is that considered finger gymnastics?
Nobody is really PUSHING the 65% form factor as you said, companies tend to make what they think is popular in the market, which at the moment appears to be 75 and 65%. There are plenty of boards in other form factor being sold (and I suspect the full size and TKL form factors still dwarf these niche smaller boards by an order of magnitude, just going by the sheer number of boards big name OEMs like Logitech, Corsair, HyperX etc... pushes out annually, and I don't see anyone complaining how hard all the big name brands are PUSHING the full size/TKL form factor). The 65% form factor itself has been around for years (the first really popular 65% in the hobby scene was the TADA68, first ran in 2016 and iterated upon multiple times since then).