It comes from the first implementation Benoit performed. We used it on many cases, carefully looking at the h0 distribution, but I do not think it was compared with a reference implementation that can be easily reproduced.

What do you think of a test performed on Normal and unrelated data, with a few targets, many (>= 10,000) permutations, and verifying that h0 is symetric, centered at 0, or even that it is a Gaussian?
I agree this would not test the actual values in h0, but at least we would be more confident with them.