I think it makes the signup process fairly simple and easy. At least, it doesn't complicate it. Email confirmations are almost standard anyway. The only difference is that by doing it this way, you don't reveal whether a user already exists with the email in question (the email is the username).
I have a hard time seeing what friction is added, though, with proper thought. If you don't require email validation but use it as a unique login identifier, then a malicious body could DOS all future users via bulk signups. DDOS required if you use rate limiting on signups. Slightly different application of the attack but still a denial of service.
Even a non-hacker could block another user from signing up by simply creating an account with someone else's email address.
If you don't use it as a unique login identifier, there's no problem at all. New users use their username to login.
This adds more friction in the signup process than I'd be willing to accept, but it does solve the information disclosure problem.