ralf
azslow3
ralf
If you enable in the preferences the automated echo for the selected track, then "none" becomes "omni" for the selected track. This is useful, because you can switch your keyboard to a track simply by selecting it.
If you disable automated echo, "none" is none and stays none. Then, you can echo single tracks and select whatever input you like, be it an explicit midi channel of a particular midi input, be it midi omni for all inputs, or be it none to silent it.
I think this a completely consistent logic. But it depends on the automated echo in the preferences. Turn it off, if you don't want Sonar to have "none" behave like "all" for the selected track.
If I disable echo and not recording... then ANY input settings becomes "none" and stay none. "None" (as none) make any sense if (and only if) whatever you do there will be no input.
Sorry to say, but current "completely consistent logic" remind me about very old joke: "To prevent infections, use condom... but more important, avoid sex" 
That's not what I said. All I said is that you have two options. Turn automated echo on, then "none" will become "omni" for the selected track, which is pretty useful to quickly change the input for your keyboard by selecting a track. Turn automated echo off, then you have to manually enable and disable echo for each track, which gives you direct control without any surprises. Pretty simple, and it's your choice. But enabling automated echo and then complaining that it doesn't know if you want it to be active or not at the very moment ...
As clearly stated in the OP, this thread is not about workarounds we all know. Yes, there is an option to turn Echo off. And when it is off, the input is irrelevant.
But the thread about the meaning of the word "None" which is always "Omni". If the Echo is off, it is still Omni, but since the input is irrelevant it works as "None", the same way as let say "Kawai DP / MIDI Ch 1" is also works as "None".
As you have written, automatic Echo (lets not call it "automated", since this word is normally used for Track Automations) is pretty useful. If you have several tracks and you change the focus to play different synth by changing the track in focus (Sonar does have easy mappable to keyboard/MIDI functions for that, but not for switching directly to specific track), at some moment you can temporarily switch to track you do not want to play. Fancy things can happened then, especially when some of Synth has MIDI output enabled. Not only some notes can be audible, arbitrary (!) parameters inside this synth can be invisibly (!) changed in case some other synth sends CC and this synth react on them. Unlike notes, changes in parameters are permanent (!). You can not "undo" them, they are not reverted on transport stop, they can be invisible. You save your project and it is "corrupted", without any way to find why.
I repeat, we know workarounds. Adding external "MIDI Loop" which is never used and setting track input to it is the (only?) way to truly set track input to "None". But "completely consistent logic" should respect the meaning of the word "None". I do not think there can be any second opinion on that...