My survey indicates that the iPhone 15 Pro series overheating issues are unrelated to TSMC’s advanced 3nm node. The primary cause is more likely the compromises made in the thermal system design to achieve a lighter weight, such as the reduced heat dissipation area and the use of a titanium frame, which negatively impacts thermal efficiency.
Kuo predicts that Apple will be able to address these problems through software updates. That being said, Apple may struggle to make too many improvements without also compromising chip performance:
It’s expected that Apple will address this through software updates, but improvements may be limited unless Apple lowers processor performance. If Apple does not properly address this issue, it could negatively impact shipments over the product life cycle of the iPhone 15 Pro series.
https://9to5mac.com/2023/09/26/iphone-15-pro-overheating-updates-fix/