I think the point being made is that movies were made for the B&W end result, not just shooting color with B&W film. For instance, fake blood in B&W was often

I think the point being made is that movies were made for the B&W end result, not just shooting color with B&W film. For instance, fake blood in B&W was often produced with black liquid. Colorizing it correctly just doesn't make sense. Or a green or blue dress can be chosen because of the way it looks on film, not because it's supposed to BE a green or blue dress.