I think it's very important that a software's GUI function in a manner that's expected by the End User. I also think most Software Developers would agree. This is why countless hours and dollars are put towards developing GUI's.
Now I agree, working with your ears and listening to how a mix sounds is the most important thing. I also think having tools that function as intended is important as well. For example the the Smart Swipe feature in Sonar, imagine on the Mute button that when using the Smart Swipe the Mute button did the opposite function than indicated by the GUI. While it's still technically usable, personally I would find it annoying. You could always propose the argument that if it doesn't work the way I like, don't use it. Fair enough and I agree. I also think it's helpful to the Developer if Users point out funky glitches in the software. In the end, it only helps to make a better tool.
All that being said, my original intent was to make sure that I wasn't misunderstanding the function of this plugin because it wasn't clear what was going on with the Threshold control. Also, if it was malfunctioning, maybe the Developer would like to know and that it would be nice to get an updated version that worked properly. If that doesn't happen, I'm not going to lose any sleep over it.