Yeah that's a BS dark pattern that drops my opinion of the site to zero.

Enjoy all the mail that you will receive now

This is why I always sign-up for something first time with fake data and a throw-away email address (I have a catch-all sub-domian, that is no longer off my main domain, for that). If it turns out the site is something I might care to return to I might then sign up with real details, or edit the initial account, if not then the email address given to them gets forwarded to /dev/null for when the inevitable spam starts arriving. I'm thinking of seeing if the wildcarding/catchall can be applied at the subdomain level, so I can fully null-route dead addresses in DNS and not even have connection attempts related to the spam.