Just my personal experience, but I've recently upgraded from a MBP with the M1 Max to a new MBP with the M4 Max and it does get hotter when doing heavy tasks (eg: video transcoding). It gets to 95-100ºC faster, uses more power, and the default fan curve is also more aggressive, something that Apple usually avoids doing.

It's still very efficient and doesn't run hot under normal load (right now my CPU average is 38ºC with Firefox and ~15 tabs open, fans not spinning), but it definitely generates more heat than the M1 Max under load. Apple still seems to limit them to ~100ºC though.