Treatment option missing from Basic Panel

As further input: LrC does not ever work in true monochrome anyway (even a B&W treatment may receive tinting / grading, and regardless of that, will still produce a RGB encoded JPG when you export - not a monochrome encoded JPG).  So using a monochrome Profile, or selecting B&W processing, or applying a desaturating adjustment, are effectively the same. The only differnce being that images for which B&W mode has been explicitly chosen, are the more easily distinguished since LrC makes this available as a searchable image attribute. 

My own habit is to apply a preset which sets 0 saturation for all colour ranges (Color Mix panel), since this method leaves all of the interface the same as when working on a full colour treatment. Going to B&W explicitly will suppress some of the colour specific controls (that one may still want to vary, in pursuit of exactly the mono conversion one wants). I replicate the same function the B&W panel would otherwise supply, via the Luminance controls within the normal Color Mix panel.

Thanks for the reply! It does seem to be a clunky way of doing things. I saw the old method in a YouTube video, and you could just select color or B&W and switch between the two. With the B&W button if I want to go back I need to reselect the grid of profiles and then select my camera, which is not as convenient. But thanks for the quick reply!