> There's literally no worse context switch than having to go into your inbox, wait for an email, then come back to the appropriate tab to complete registration or login.

Then it's something maybe the customer isn't interested in the first place. Most of the time mail just works for me only issues are sometimes greylisting and it takes hours.

I can understand it from the company side, but not sure how well it really works when someone use a mail app on mobile and on desktop not even logged into the mail account.