I'm using PlayFab Unity SDK. According to the docs (and confirmed by experimentation), AddUsernamePassword  requires a username AND an e-mail address. However, you can create a PlayFab acccount with only a username OR an e-mail address by using RegisterPlayFabUser .
Is there a reason for that discrepancy? Is there a way to only add e-mail+password to an account?
I'd like to simplify the register form for my users, so I don't want to ask for both usernames and e-mails. I tried to pass an e-mail as both the username and the e-mail, but it isn't accepted because it contains invalid characters.