So true on so many levels. Stiffness vis-a-vis softness of leather uppers on J's can only be fully realized ON THE COURT. When you have stiff leather/lack of padding on the ankle collar and you tryin to make lateral cuts, you can EASILY feel the difference as opposed to soft leather and/or thicker padding. Tech also plays a huge part on performance on the basketball court, obviously.
When you only rock J's for casual wear, the only thing that matters when it comes to comfort are the tech and the soles.
How is then that you can ask everyone who has owned and worn a AJ4 white/cement from 2012 and a pair from 2016, which have the exact same tech(midsole especially) and they will tell you the huge difference in casual wear comfort?
Another good example would be the Air Trainer II SC OG QS from 2011 vs all the GR releases of that same shoe. The QS versions had "softer" leather vs the GRs that had a very stiff material. The rest of the tech on the shoe was exactly the same. Ask anyone who has owned both and they'll undoubtedly tell you the difference in comfort in casual wear.
That's like saying if you put synthetic leather on a pair of Adidas Boost instead of the prime knit there would be no difference in comfort. Of course the uppers matter. Your foot is still flexing regardless if you're doing something strenuous vs just casually walkiin.