Silence Unknown Callers not working in Catalina

I have Silence Unknown Callers turned on on my iPhone, yet my Macbook rings. Is this an overlooked bug or do I need to change a setting?

Related question: when I receive a call on iPhone, I can click the power button once to silence the call (with the call still usurping my screen, unless I reject or accept the call). How can I silence a call on Mac without Accepting or Rejecting (not waiting for the call to finish ringing). Older threads suggestion hitting the volume down button (I've tried volume up & down) but it doesn't work. I know I can mute computer audio, but I might be on a call (different program) at the time and can't mute.

Advice appreciated.