Apple has acknowledged user complaints that iPhone 15 and 15 Pro phones are overheating, reports Forbes, but said that contrary to speculation, it has nothing to do with the phone’s hardware design. Forbes noted an update to Instagram has already rolled out with version 302, released September 27th, to address some of the issues.
That implies a problem with Apple’s scheduler and/or thermal management
The kernel should never allow a user space processes to overheat the hardware