Data Protection shouldn’t be a relevant issue - at least not in the sense that it forcss them to delete accounts. When you process data under the GDPR, you have to identify a lawful basis.
I assume that transactions through the eStore would be handled under the contract basis, with the hosting of the game in the library forming part of the contractual relationship. That would enable them to maintain an account for as long as the contractual relationship persisted.
That basically means GDPR doesn’t force them to close an account, they close an account based on their policies because they choose to. That’ll be based on their T&Cs, so things will fundamentally circle back to whether their T&Cs are legitimate and lawful.
It is possible that a data subject could potentially raise a claim for damages under the GDPR, on the grounds that the deletion of their account is a breach of contract that amounts to an availability data breach.