I’m not a fan of the full screen page switching animation (the new page sliding on top of the old one), but that may be a matter of taste.
Typically, on Android, there’s just an arrow animation when swiping to go back and that simply works on both sides without causing confusion in the motion.
You’re right about first party apps limiting it to the edge, I can’t think of any either right now. But YouTube, Telegram and others don’t.