Maybe I am missing something but I have never seen anyway to shut off the color channels via the Canon software.
The result, I believe as you have pointed out several times, is that there is always some degree of metameric failure ( hue differences under various light sources) when using the Canon driver. Unlike with the Hp Z driver software, when you send a grayscale file to the Canson driver it is still color managing it and adding color inks. Why that is I don't know. Are you saying you can shut that off in the Canon driver and print grayscale?
I have never been able to print out of just the gray and black channels without using TBW. I have no issues with it once it is set up. I have pre-made linearization curves and it seems the easiest clean monochrome I've ever used, once the curves are made and that's vastly easier than QTR or Studio Print. My I-1 Pro2 interfaces fine with it on the Mac Platform. But I don't know about updates to the latest Mac OS since I'm not using it.
john
Actually by dialling in a correction in the driver with the B&W mode (refined with a grey card as above), I found it very usable and have been making use of it for several years ... YMMV it would seem ;-)
TBW is good, but suffered noticeable usability issues from my POV - I'm hoping they manage to have the updated version ready before the PRO-2000 has to go back