I think the core problem is that black and white's disappeared as a viable option for all but the smallest arthouse films. So these filmmakers might have originally wanted to make a black and white film but went with color for commercial reasons. Then, when given the chance, they jump at using the film's prestige to let themselves create the monochrome cut they originally envisioned.

But since these are all great directors, when they had to shoot in color, they incorporated that into the film's design and used it to great effect. The color is built into the film's DNA even if, absent commercial demands, it wouldn't have been their preference when they first thought of the idea. So even the director's best attempt at creating their "preferred" black and white vision ultimately feels like an imposition upon the film's basic nature.