Same here. Sounds like a couple social media apps are common culprits (gasp!! Whodathought!?). I can’t recall who I was listening to but they took temperature readings on both a 15 PM while using Instagram Anna then on a 14 PM and both had very similar temperature spikes.
Not discounting that people are seeing issues..MKBHD has his temp spike for a few minutes while in airplane mode listening to Spotify on a flight yet it didn’t while outdoors in 90+ degrees F heat in Florida at full brightness. My guess is there are some isolated software bugs in the OS that Apple will work on in the next OS update.
I’ve personally not had any overheating issues either. And I’m certainly aware of what a warm phone feels like considering my other phone is a Pixel Fold.