On Signup, new user can enter in different email/repeat email address in an edge case scenario

I’m fairly new to Auth0 so any pointers are welcome. My company uses Auth0 for login and signup. We are using the classic (old) login signup experience. We have a bug for an edge case where the user attempts to signup, enters in an existing email and repeat email, then gets an error message that the user already exists. This is all as expected so far.

But then the user enters in a different email address, but forgets to change the repeat email field. We would expect that the user be warned that the email and repeat email do not match. What happens instead is that the a new user is created anyway.

So to fix this bug, I am looking for a way to inspect or edit that logic, but I suspect that I cannot, at least using the classic experience. This is a case that I am hoping I am wrong and that I just have not stumbled across the solution yet. Any ideas here?