Upload & Sell: On
It would be nice if Adobe could separate the files as you suggested, akin to using metadata to sort.
But I think this was an avoidable error that is unfortunately time-consuming to correct and I am not aware of an easy fix.
Why were you trying avoid adding keywords? It is painless to select a slew of images and attach keywords. A bit more time-consuming to add them individually as you go, but I think its the best solution going forward.
What could speed up a fix now? Not sure, but I might go to library mode, find All Pictures, set the thumbnails to the smallest size to view, set preferences to build lower quality thumbnails. Then I would select the BW's and apply whatever filtering or collections method(s) you prefer. Colors, keywords, collections, etc.
If you do learn of an easier post hoc fix, let us know.