That would be a bummer, because I have a situation where I need several buttons working as a radio group, but where "none selected" is a viable option, just like physical radio buttons. And yes, I'm old enough to remember those things.
Some old radios could be shut off by tipping a radio button so light, that any active button comes out.
If you want to do a simular thing that in VMD, you could extend your toggle button group with an additional toggle and set that unvisible. If you set that toggle on with SetValue(1), the others will go off.
Thats the sort of behavior I had in mind. I've temporarily solved it by adding another (!) button, but just leaving it visible. I may change it to work your way, although having a true multi-state button would obviate the need altogether. Thanks for the tip.