I like the feature in general (first signup step with only email and code), but it has some rough edges:
a) the login and signup should be seperate config
b) hiding the username entry on signup form should be an extra option, since the usernames are still am important communication feature random or counter usernames look quite odd
c) strange enough the random usernames worked on my site for some spam signups (unverified user entries) but not for two real users, they both got “user1” and “user2” as names, ugh. (Not sure whats the difference is between the spammers and the users)
d) for login can it be an extra button, maybe one which sends a email with a magic link and a code. I dont see the need to seperate this.
e) the docmentation should make it clear that it removes username form (or better, not remove it)