I agree that it is still a little confusing, but getting better.
The Emcon On/Off buttons set the default mode of the module when you switch from Out of Emcon to IN Emcon. So, if the module is set to Emcon off, and you go INTO Emcon mode, the module will turn off. And I think it remembers whether it was on or off when you went in, and restores that state when you come out. The Connect/Disconnect buttons will manually override the Emcon mode state that you are in to turn the module on/off.
I think it might make slightly more sense to have a Default On/Off toggle for both Emcon On and Emcon Off modes. That might be clearer to the user. You could still manually override with Connect/Disconnect. But whenever you switch in or out of Emcon, the module goes on or off depending on the toggle for that mode. Probably simpler to code, too.
Module On | Off
Emcon | ( ) | (x)
Non-Emcon | (x) | ( )