I was a little confused recently when I tried to reset my password. The automatic autofill with the username makes sense as long as it is sufficient to reset the password. However, if “hide email address taken” is activated, the email address must be entered. It was more confusing than helpful for me that my username was there when I had to enter my e-mail.
I totally understand that the autofill is helpful when “hide email address taken” is disabled, and it’s helpful too if you enter the e-mail address into the login form before clicking ‘I forgot my password’. So maybe if hide email is enabled, autofill should only happen if there is an @ in the e-mail/username field.