I'm traveling to Europe right now and had to install WhatsApp, and this absolutely infuriated me. You cannot start new chats with anyone (on Android at least) unless you grant it the contacts permission. I'm sure other things are limited too, like you say.

Workarounds include having the other person message you first, or manually typing wa.me/+number into your browser.

Slightly more info: https://android.stackexchange.com/questions/229390

It is clearly an invasion of privacy and huge overreach by FB.

Install OpenContacts from F-Droid and store your contacts there.