It's a good puzzle, and the analysis dealing with it is correct.
How is it even possible for A and B to be indiscriminable, B and C to be indiscriminable, but A and C to be discriminable? It seems like if A and B cause the exact same conscious thoughts (or whatever you're updating on as evidence), and B and C do, then A and C do. I think in practice, what's more likely is that you can very weakly probabilistically discriminate between any two adjacent states.
If it's worth saying, but not worth its own post, even in Discussion, it goes here.