That would surprise me. I don't recall having to change my iPhone's region after moving to Japan. Transport IC cards in Apple Pay have "just worked".

I am vaguely aware that some phone manufacturers silently remove certain NFC hardware (or disable some driver) in order to avoid paying Sony patent fees. Apple doesn't seem to do that, though.

There were iPhones with Japan-specific hardware for transit cards in the past but as of a couple years ago, all iPhones have been compatible.