Max for Live Device Type? What does that do?

I see this setting in the project inspector, but can't figure out what difference it makes. For most of the Max for Live devices I have opened for editing, this setting doesn't even seem to be used (i.e. for Max audio devices, it isn't set to "audio", and likewise for Max MIDI devices - I think they're all just set to "none").

Even though the reference guide page for Project Settings shows this setting, it doesn't mention what it is used for. I've even tried changing it for Max audio devices to "MIDI", and vice versa, and saving the patcher, but it doesn't seem to make any difference in how they can be loaded in Live, or where they are listed in Live's browser.

Can someone please shed some light on this?

And on a related topic, what makes a Max patcher able to be loaded as either an audio or MIDI device in Live? I notice MIDI devices will only load on MIDI tracks, whereas audio devices will load on any track.

And lastly, I modified a MIDI device to do some customized mappable LFO control for live device parameters. How can I convert it to a Max audio device so that I can use it on audio tracks as well?