I still question the premise that battery performance info can identify individuals out of millions of users.
Sounds very ambiguous.
More would be easily gained by IP address in most cases.
By itself, that is probably true. But used in conjunction with other information, someone may be able to pinpoint down to which device you are using.
It doesn’t provide identity theft, it provides tracking. Because the call returns your percentage of battery charge and the estimated time left of use in seconds that’s a fairly unique combination that can be used to follow you through hotspots. Add that to your cookies and web activity and they can know a fair bit about you.