It’s been a long known fact that it does lead to increased battery wear on Android. A lot of that is due to the excess heat it provides. I’ve never fast charged an iPhone, but I’d imagine If the temperature is close to that of the stock brick that it wouldn’t be that harmful.
Theres some basics to li-ion that have been know for a while.
Heat= Battery degrading
Faster charge= more heat. Apple has not been able (and has not even tried to claim) that they suddenly magically reinvented the battery. They HAVE publicly stated that once your battery has degraded, so will your performance.