It is personal data regardless of how it is used. The only question is if that use of personal data is permissive.
Using it for user analytics, which is neither required to run the service, nor in the users interest, nor reasonably expected by the user, is almost definitly illegitimate use.
Using it for user analytics, which is neither required to run the service, nor in the users interest, nor reasonably expected by the user, is almost definitly illegitimate use.