Paypal enrolement seems to get information from Paypal about users address registered at paypal and paypment process used in paypal. All these information are not visible via interface.
Storing this data even if they are inviisible breaks GDPR in some situtions.. Specially finance relevant data can be sensible special categories of data.
If such data re not visible in Moodle and there is no need to use theme they shouldn't be stored in Moodle.