This isn’t a placebo, in my opinion. I have not once had to repeatedly double-tap the back of my phone to lock it in the past 24 hours. When the phone wouldn’t lock, I used to try tapping harder on the back several times—it was rather awkward when I did this in public.
I have no doubt that Apple has improved the double tap behind closed doors. In a few days, I hope I’m not mistaken and end up feeling like iOS 16.