Which isn't foolproof. I just tried to change my Apple ID password[1], and the password manager will only auto-fill the password field, not the verify password field, even if you invoke it with the cursor in the verify field. The only option is to copy and paste the password (or manually copy a 64 character password).

[1] I'm fairly sure I've copy-and-pasted my Apple ID password recently - I had to reauthorise my Apple ID (I think I was changing payment details), and there was no option to use the password manager (might be pre-iOS 13, so I'm not sure if that's still the case).