Sure, email addresses can be revoked. On any given day, for a Normie, this is a 0.0001% chance that this will happen. On any given day, for a Normie, the chance that they will misplace their nsec (or never even understand that they have an nsec, in the first place), are like 10%.
No, you got it correct. I guess my question is are the user’s sats safer using an email address provided by a centralized service that can be revoked?
https://www.pcmag.com/news/journalists-hacktivists-proton-mail-reinstates-suspended-accounts
Discussion
So you wouldn't consider this even as a backup or alternate 2FA method for that reason?