15 pro max 512GB here.
Been using it for 2 days, during setup restore and charging, of course it got hot, that I can accept.
But after that was done yesterday, today I took mine out with a normal Sunday usage pattern. Not even touching it much, take occasional photos, use GPS, syncing with Watch as I did outdoor exercise; the battery seems to burn fast-ish, and the heat is not good. I came from 13 pro and 13 mini, and never imagined a pro max line's heat behaviour can be reduced to be similar to the mini. With such a big chassis you would think it helps dissipation, but no, the back glass around the A17 pro chip area is VERY warm. In fact if I take it out of a MagSafe charging session, that area is BURNING.
Please do not dismiss this issue as hyperbole, I have been using iPhones since 3G, and never had an experience as bad as this, especially on the flag ship plus size. I have already seen the "please wait for your phone to cool down before resume charging" warning at least 3 times now.
P.S. in my location the current climate is still hot-ish, today the hottest moment was probably 32 degrees C and I was outside in the sun. But this "overheating" behaviour also happens when I was in my room, MagSafe charging with the windows totally shaded.