You mean, if you format the email in the right way, you can get your email alias to send an email to someone, before they send a single email to you?
Well I can't tell in how many ways that can be harmful, but for example if Bob is tricked to click to the legit link from the website and enter his personal information, then I can change the alias to my own email, reset the password and have full access to Bob's verified account, so yeah, that's one big flaw IMO.