You are not wasting charge cycles by leaving the battery plugged in. it is not being held at optimal charge for storage but it will last a lot longer plugged in.
It would be the worlds stupidest engineer that would design a power circuit attached to a potential class d fire hazard that had access from anything other that possibly contact pads on the controller itself. If i were a bad actor and the os has a way to access the charging circuit i would firebomb your house by telling the controller the battery is empty and have it over charge. This would be bad.
Note: I see that apple may have done the dumb and i am facepalming
Join the hive mind. Rust is life.