> Lack of transparency makes it impossible for users to exercise their rights under GDPR. There is no way to verify, correct or delete marketing categories that have been assigned to us, even though we are talking about our personal data.
> Under GDPR, processing special category [medical information; political affiliation; religious or philosophical views; sexuality; and information revealing racial or ethnic origin] data generally requires explicit consent from users — with only very narrow exceptions, such as for protecting the vital interests of the data subjects
The last quote is particularly troublesome, as Article 9 GDPR  is explicit about this: processing this data is prohibited by default, and none of the exemptions seem to apply even by a stretch of imagination.
Assigning such labels may be the norm from the Ad industry's point of view, but that is simply no longer possible under the GDPR.