Hey, I have some experience creating intentionally suspicious Twitter accounts.
There is no phone number requirement. They're just as happy with an email address.
If you provide neither of those, then your account functionality is restricted (with a big obvious banner showing at the top of every page), but you still don't get blocked.
Once I needed to create several accounts at once and then have all but one of them follow the last one. Those accounts got blocked, but it's hard to blame Twitter for that.
There is no phone number requirement. They're just as happy with an email address.
If you provide neither of those, then your account functionality is restricted (with a big obvious banner showing at the top of every page), but you still don't get blocked.
Once I needed to create several accounts at once and then have all but one of them follow the last one. Those accounts got blocked, but it's hard to blame Twitter for that.