dawt I found the same thing, a few people have claimed call screening works but I have experimental a little bit and couldn't get it to work, even with google play, phone app, device intelligence and AIcore having full permissions. All the pixel features come up in the google dialler settings menu but they don't work.
I also don't have the option "on device genAI features" available in the AIcore app info as "Beeeee" claims to have. I am starting to think the Google phone app needs to have the preinstalled flag to operate with the pixel exclusive features. I should mention I'm using a Pixel 10 Pro XL. Otherwise, I'm loving GrapheneOS!