An activist's lawsuit claims that the Android "advertising ID" is personal identifying information under the GDPR.

Victory would require Google to get free and informed consent for identifying users that way.

When Google claims that it "cannot identify a user from per advertising ID", I suspect that what that really means is that Google cannot directly identify a user from per advertising ID alone. I suspect that correlating databases collected about that user and indexed by the advertising ID with other databases about per, it is possible to associate per advertising ID with per name with a high degree of confidence.