Can you limit incoming calls to “contacts only” on adult’s standalone Apple Watch??

We recently purchased an Apple Watch Ultra 2 for my elderly father in law, who wanted a cellular device for emergency purposes, but would have lost a phone in minutes. Since it is stand alone for him, it had to be set up with someone else’s iPhone. Lucky me for being the “techie” of the family. I created him an Apple account, set the watch up, etc. I am trying to set communication limits so his watch can only be called by family in his contact list. Everything I’ve read online says that can be set in the “screen time” settings. When I go there however, his device is not listed. I have restarted both devices and completely erased and repaired his watch to no avail. I’m even listed as his “guardian” through the Health app thinking that would help. Short of creating a new account for him where I could create a DOB indicating he is a child (which wouldn’t be great if anyone needed is medical ID info in an emergency), does anyone know how I can set this watch to receive calls from contacts only?? I’m pulling my hair out here!