I've never been able to sign-up for a google account without entering a valid phone number. Even typing 555-5555 it will state it needs a valid phone number.
I had thought this was the case as well, but just tried signing up for a throwaway google account from the US browser homepage and it seemed to go through without a phone number or alternative email.
It probably depends on your IP address and how many accounts were registered using it (if your ISP uses NAT then many users share a single address) and maybe other factors like country etc.
From Dubai. Didn't need to enter a phone number or a recovery email to create an account