Workarounds to Restricted #s
Not sure what the Android looks like, but at least on iPhone, with some effort, you can set the voicemail notification to sound off a ringtone instead of a simple chime/ding.
I have my do not disturb set such that Arcos (# and APP which also has a notification sound), family, CS (only for the short call version), but also the Phone "app" are on the allow list. In iOS, the "Phone" app winds up being the notification source for voicemails. So, after allowing notifications from the Phone "app" on your DND settings, leaving sound on (bell not crosshatched), and setting up an obnoxious "notification" tone for voicemails (via garageband app is the only way I am aware of), even though the call itself might not ring due to unkown #s, any voicemail left will "ring" you so long as the voicemail notification comes through.
Works great for me as I haven't had any situations where I got a voicemail late at night/early AM that wasn't pertinent. I've heard stories of CNO calls for hotel changes or trip assignments way earlier and at worse times than neecessary, but I wager anyone with the phone set on to allow CNO rings at night in hopes of an IA would have that problem either way. Such CNO nuisance voicemails may be mitigated via CNO restrictions on Deltanet.