For this to happen Apple needs to know your new npub or nsec somehow.
Since npub/nsec are generated by the app and hopefully with some randomness, Apple won’t know what they are unless you tell them, or unless they are monitoring your activity and all of nostr well enough to piece together their concept of you + the nostr concept of you (your nsec/npub).
It seems like they are doing neither of those things - though they do know that their concept of your downloaded a Nostr app.