The anonymous e-mail that Sign-In with Apple generates forwards to the e-mail used to set up your Apple ID. So it's not like it's a random e-mail that acts as a /dev/null.
This is by far the biggest selling point of Sign-In with Apple for me and I will continue to use it, and continue to not use apps that don't support it. I have plenty of e-mail aliases, but having an alias auto-generated for you is very convenient, and not having to generate a secure password is also very convenient.
The day AnyList gets hacked (not saying it will - but it's highly likely, the way security has taken a backseat due to "features") then at least my personal e-mail and password won't be there for every hacker on Earth to see and try to spam passwords to get into all of my other accounts.
This is by far the biggest selling point of Sign-In with Apple for me and I will continue to use it, and continue to not use apps that don't support it. I have plenty of e-mail aliases, but having an alias auto-generated for you is very convenient, and not having to generate a secure password is also very convenient.
The day AnyList gets hacked (not saying it will - but it's highly likely, the way security has taken a backseat due to "features") then at least my personal e-mail and password won't be there for every hacker on Earth to see and try to spam passwords to get into all of my other accounts.