You send information to the apple address, that's what its for. You can still send it invoices or a magic link, the user gets it and clicks on it, nothing is changed in that regard. The difference is they can turn off that email address and never hear from you again if that is what they want.
Stuff sent to the fake email address will be forwarded to the user’s real email address, from what I understand. So you will still be able to communicate with them.