Why iphone 12 overheating easily when i play pubg mobile since ios 15 update?

hello, i used iphone 12 since december 2021, i regularly play pubg mobile on lower graphic with 60 fps settings. everything was fine until i updated the device to ios 14.3. The device became easily overheating (just for about 15 minutes of gameplay, the device already overheating).

why on ios 14.2.1 or 14.3 the issue never occurred?

Now i feel My iPhone it’s very bad because when I play PUBG ifeel my iPhone hoter