Unlikely because services in the EU have to be offered without barriers to everyone across all member states.
Because now I live in an EU country that had (and has) foreign products and services, typically of US origin, that are not officially available in my home EU country, like for example Xbox GamePass for console. Was same with Nextflix till a few years ago. Same with AMEX cards.
So NO, you can definitely provide your services only to specific EU member states if that's what you wish, they can't force you to sell in all countries.
I.e. streaming providers can't stop you from watching Germany exclusive Netflix content when on holidays in Greece using your German Netflix subscription (only free/ad supported services are allowed to do that)
Basically, Apple can stop selling developer accounts in Italy if they wish. They might run into issues on discrimination grounds, but it would probably be a long fight.
However, they can't prevent an Italian developer from purchasing a developer account from another EU country.
https://eur-lex.europa.eu/EN/legal-content/summary/geo-block...
(Also, I would assume Apple would require a developer to have a legitimate physical business address in a country where they allow developers. I don't imagine this would be an easy transaction.)
The opposite -- Italian law governs because the developer is Italian, even if the developer makes the purchase in Germany -- seems untenable even by European standards.
The point of this law is that it must be an easy transaction. I'm sure there are many companies not following the law properly and getting away with it, but it does seem like Apple will be watched closely to ensure they are doing everything correctly, as a result of their malicious compliance with every previous ruling.