However, Autochrome and Dufay do the same, and with transmitted light can reproduce whites, but when coated on reflection support appear black and white with some color spots. Same applies to color inkjet printing if done incorrectly. This is why older color printers did so poorly and why modern ones do so well by comparison. It is also one reason why color printing is effectively so slow.
And, if you wish to take your idea further try this. Process some E6 films with bleach bypass. then look at them. They are black even by transmitted light. And, do the same with color neg film and you will get desaturated color. You have effectively added a B&W image to a Subtractive color image. OTOH, that same B&W image in an Additive photographic system is essential to getting any image at all. And, in digital printing or standard color print systems for magazines the C/M/Y/K is essential but for another reason.