Yeah, but effectively that's what Your Mother was asking for, a counterexample for the thesis that multidimensional hashes are safe. . . . So of course YM's "aka" is not correct in mathematics.

Your first point is well-taken, but yes, it was the "AKA" that prompted me to underscore the difference.

I might not like gratuitous pedantry, but that's only when others do it. ;-)