Yeah, it looks like only the system menu triggers that message. I haven't seen it in another case, but that can technically happen.
If you want to look into it (you don't necessarily have to know C++; I started working on Dolphin with absolutely no C++ knowledge), you'll need to figure out why the emulated software doesn't ask the STM to shut down when the last Wii remote is disconnected.
And that's the only thing that is required to make this work, because I have already made the STM stop emulation when requested to.
If you want to look into it (you don't necessarily have to know C++; I started working on Dolphin with absolutely no C++ knowledge), you'll need to figure out why the emulated software doesn't ask the STM to shut down when the last Wii remote is disconnected.
And that's the only thing that is required to make this work, because I have already made the STM stop emulation when requested to.