There is no need for your phone number. The review does not require you to provide any personal information. On the contrary, they ask you not to include any personal information.
So how exactly do they fight spam or fake reviews?
It's a little confusing because somewhere else they say that
Submit your case information to opt-in for professional support in recovery.
Your review goes live after a spam detection check. Rest assured, your personal information won't be shared in line with our privacy guidelines.
In this case which personal information are they referring to if not the phone number, email addresses or names?