If someone hasn't used their account and sign up again, they won't get a new person email and its an absolute nightmare. It should go "you already exist - maybe reset your password". but also check if that'd work with not yet used accounts.
I suspect the reason why the current behaviour is like this, is such that spamming the form won't effectively DDOS a user's email etc/ make it possible to work out which users have accounts.
If someone hasn't used their account and sign up again, they won't get a new person email and its an absolute nightmare. It should go "you already exist - maybe reset your password". but also check if that'd work with not yet used accounts.