An update for 15 Pro owners:
Since disabling Background App Refresh on Instagram, Threads, and Snapchat (which I barely use them other than Instagram, so they didn’t need to be on anyways), my phone’s heat levels are what I would expect and on par with my 14 Pro, except for one specific situation:
YouTube app playback, especially with Picture in Picture, seems to generate more warmth than I would expect. This doesn’t seem to happen with YouTube in Safari or other apps that play video.
It’s not getting hot, but it is getting warmer than I would expect/my 14 Pro doing the same task.
I think the heat “issue” is a software issue with certain apps and the system. The phone will likely just always feel warmer if you’re touching the outside titanium frame (stainless steel is always going to feel cooler to the touch than Ti or Al), but so far the cases of my phone getting abnormally warm are isolated to a few third party apps.