I believe the important distinction is between 'having access to phonebook for calls and chats' and 'datamining phonebook for the needs of Facebook'.
Signal (the foundation) does not get to use my phonebook even if Signal (the app) does.
Made the switch yesterday. Hope this will be a turning point for Facebook
And that's why I recommend Jami - https://jami.net/ - you don't even need to share your phone number or email id to use it.
Asking repeatedly for information that is not necessary is a red flag. It is suspicious, to say the least, that Signal is not censored from Apple’s Appstore.