I encountered a same problem with this question. I'm using a wired external accessory in iOS 15.2 and app is killed after doing something in background mode for 30 seconds. I already checked External accessory communication and Background processing in Signing & Capabilities tab. Fortunately this issue is not occurred in iOS 14. (Hope this help for solving this issue) Please anyone give me any clue.

@jay_shah01 I'm looking for a same subject with you. As far as I've found about this there is (probably) no way to manipulate an interval or a frequency of updating pedometer data. So I'll find out a detour of not using interval manipulation of queryPedometer but I'll follow it up if someone knocks the door of this article with having an idea for it. Hope you have a desired result for it as soon as possible.