@Zimmy, it is more or less suppressed yes. The program hooks into the dbus of GNOME calls to listen for new calls and makes a bunch of decisions based on what it sees. If you are looking at it, it flashes on and off.
I can’t make it hang up any faster/fully suppress the notification without actually being a part of GNOME calls. I intended it to be easy to merge in GNOME calls, which is why it’s written how it is (C, GObject). I already talked to the call’s devs, and I am waiting to see their interest in merging this code into theirs.
I more or less scripted how I respond to calls from unknown numbers (i.e. did they call twice? is it from a prefix I recognize? is it a blocked number?), and I added a settings file to have folks tailor it how they want to.
If you have other thoughts, feel free to file issues/thoughts/MRs/etc.
EDIT: In my very scientific test of sticking my pinephone in my pocket and calling it, I did not feel anything. I did get a “missed call” notification.