If you do not implement account creation, then you're unlikely to be held responsible for account deletion, as a user would reasonably understand that your app is not responsible for creation or deletion of accounts.
EDIT: Elsethread, someone asked "What if I create accounts on the blockchain?", and since it's possible you'll come around to that idea next — the app would have to interact directly with the blockchain, so you'd probably get rejected for a whole array of reasons, such as but not limited to that you're storing account data on the blockchain. And I wouldn't envy you trying to explain why you shouldn't be continuously fined for GDPR violation in the EU, either.
This is kind of a bizarre thought to me. You think anyone who provides software that - without involving any services hosted by that person - should be liable for what users do with this software? If this were to hold up in court (which I'm confident it wouldn't), then open-source software would be done.
Or is this a problem of terminology? In the scuttlebutt case, there is no actual "account" - just a key. Maybe one should simply replace the string "Create account" (if there is such a string) with "Generate key/identity".
I realize many people are heavily invested in the Apple ecosystem, especially since Apple encourages that with the proprietary integrations between their different devices, but there's a point when one should realize they have a choice. It's a walled garden not a prison.
As an app developer, this isn't a choice I get to make. I myself have used Android ever since modern smartphones became a widespread phenomenon.
There’s a lot of arguments that people will make about whether this is justified or not, but from a plain rules standpoint, that’s not a permissible data management strategy if you want to publish an iOS app through Apple’s store.