This looks suspiciously like OpenID with the identifiers changed from URLs to email addresses and updated to use modern pop development tools.
I really liked OpenID, even though it had a few issues. The best part was that you could put a few HTML tags at the URL you used as your identity and delegate the authentication - but not the identity - to a 3rd party. Because you controlled the identity, you could drop the 3rd party and use someone else (or implement the OpenID protocol yourself locally) just by changing some tags.
If "Passwordless" can provide this can provide the same level of autonomy, it could easily become my authenticator of choice.
It looks like it's tied to an email account? Slightly annoying, but trivially worked around if necessary.
I don't know how it's implemented, but I see no reason why adding/removing emails to/from an existing account (while logged in) wouldn't be trivial to implement.
The only thing you need to be careful with is to send a notification to the email being removed, send notification to all emails when a new one is added, and enforce some kind of expiry period before a removed email becomes inactive/added email becomes active.
It is not necessarily linked to an email account. It's up to the lookup middleware that has to be programmed by the implementer how to translate the login into an email address / phone numbers
I really liked OpenID, even though it had a few issues. The best part was that you could put a few HTML tags at the URL you used as your identity and delegate the authentication - but not the identity - to a 3rd party. Because you controlled the identity, you could drop the 3rd party and use someone else (or implement the OpenID protocol yourself locally) just by changing some tags.
If "Passwordless" can provide this can provide the same level of autonomy, it could easily become my authenticator of choice.
It looks like it's tied to an email account? Slightly annoying, but trivially worked around if necessary.