No, I don't think that this has anything to do with GDPR or data protection, this is merely an interpretation of the Tax code.
It is well established that a commercial transaction made through a barter bears no difference against the same transaction made through exchange of money.
The barter may be through exchange of goods or services.
There is a by now historical sentence here in Italy about the organizers of a contest and a local newspaper[0].
Basically the newspaper published about the contest (not as a news article but rather as an ad, including the rules, forms and what not) and the contest organizers had on all their printed material (forms to sign in, posters, etc.) a note like "in cooperation with newspaper name".
The Tax office considered this "exchange" as if it was two operations, one in which the newspaper sold publicity, and one in which they bought publicity on the contest material and it went through all the various courts until the Cassazione confirmed this approach.
That was a case between two entities subject to VAT, in the case of citizens (not subject to VAT) and an entity subject to VAT (Meta in this case) the part subject to VAT should (in theory) emit an "auto-invoice" and declare the VAT on the value. (or at least this is how I understand the matter, probably there will be more details in the news in the next few days/weeks).
[0] (in Italian):
https://sentenze.laleggepertutti.it/sentenza/cassazione-civi...