No idea, but these things never know if it's a real phone number or your phone number and they aren't going to ring you.
When asked for a phone number that I don't want to give, I first try just 0s (It's 10 here so that would be 0000000000) That usually works.
I also keep a list of old, disused, numbers and I have used the number of the local post office.
Hope that helps
Re: "fake" numbers, NIST atomic clock is a favorite. (303) 499-7111
That said, aren't Apple IDs two factor now? If you don't have or lose a trusted device, and have no number to call, locked out of your Apple stuff when they want to send a 2FA code. Or unlock your account.
EDIT: yes, as long as you have your Mac, will get a code sent to the Mac when signing in, but still...