[old_tv_nut]

I suspect the switch was only in the Super chassis, as maybe its color killer was not as reliable as the Deluxe. Hopefully, owners never used it, as it could lead to nuisance service calls if someone turned off the color and forgot it.

Edit: an annotated copy of the schematic (I believe it's from the ETF site) shows in red pencil modifications to the Super color killer circuit, so I guess there were problems.
I don't have a video source without a color burst, so I can't test my set, but I'd guess the trouble would have been opening up the color circuits on noisy fringe-area monochrome signals.