Because the GDPR isn't about any specific technology, but concerns any processing of personal data:
Edit: Huh, I stand corrected I don't know if this would count as personal data.
Edit: Huh, I stand corrected I don't know if this would count as personal data.
The post says that they don't combine datapoints because that would negate privacy.
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.