ahhh....good eye. I wasn't really looking at the binding too much, just the boots. Size 9 boots should have no problem with his board, but the L bindings might be too large for his boots.
Yeah good catch.
Large is def too big for a size 9. You won't be able to center your foot with the unibody baseplate. It's why you have too much heel overhang in the pic.
You'll have to get the right binding size. You can't go wrong with any of the those listed above.