All indications point to Apple restricting background timeslices for programs to reduce available compute cycles. Keeping modern chips at top speed for processing in bursts and then sleeping is actually more power efficient than throttling and allowing continuous calculation ( https://en.wikichip.org/wiki/race-to-sleep ) At nominal TDP, the A17 will drain an iPhone 15 battery from 100% to 0% in under 3-4 hours, even with the radios and screen off. The only way it can usefully function is to be in sleep mode most of the time and some processes were getting more time slices than would allow that.