the fact that the black queen must be on a1 rather than a2 when white plays nxb3 explains why 2.h4 does not work. similarly, if the white knight takes a more direct route to the b3 square with 8.ng6 qa2 9.ne5 qa1 10.nxc4? qa2 11.na5, black can lose a move with 11...c4! 12.nxc4 qa1 13.na5 qa2 and there is no mate. this kind of precise timing is quite a common feature in this type of problem.