That’s just how federation works. You’ve federated with an instance/user so now your self hosted instance will be updated.
Is there a reason you’re concerned about the requests? The payloads should be relatively small, and unless you’re running on some really old hardware, one request a second with a small payload should not have any noticeable impact.
Xiaomi makes Android phones, what would they get out of trying to make iPhones look better.
Most likely explanation is the voltage difference people have mentioned