It does. I’ve been using it, I tested it, it works. They just get the info that I am “currently unavailable” and I get SMS with info on who tried to call me when I was “unavailable”. Just like airplane mode, but I get to keep data and SMS.
2G will be used only for emergency calls.
4G/5G doesn’t support traditional voice calls like 2G/3G did. Only VoLTE, VoWiFi and VoNR which are a total mess with lack of one universal standard. (And you can disable them, which is the point of my comment.)
But they can try, if that’s what you meant.
Look at the bottom with server count. Likely something screwed up there, and when those instances were suddenly returned, the user count was added back before being subtracted when they disappeared from the data.