>>7611200
>Cherry-picking cases a bit, though, isn't it?
no. 2-tone works great when you are trying to teach the very basics of separating light from shadow on geometric wood blocks or fruits/simple objects in a classroom lightbox like these:
>>7610516
>>7610517
>>7610519
>>7610520
>>7610521
>>7610732
but every single one of these examples use some form of graphical abstraction to pull forward/push back a shape (outlining with white/black against an opposite background shape) or using an abstraction of midtone (hatching), which is not the exercise bradley is describing
for completeness, these >>7611026 are great, but some use an additional grey tone for clarity, and >>7611153 >>7610422 are the only ones that did the exercise "correctly"
it's highly dependent on the photo/studio ref you use
tl;dr - the exercise is fine, and it's needed for many beginning artist's to get a handle on value grouping, but it's so limiting that you should move on after like a week of playing with it, because it becomes both trivial to do and provides little further learning value, which is exactly what bradley elaborates on in the full thread.