It depends on your motherboard / BIOS. Some work with only one IDE port, some don't! ldotsfan, scullc and fwz didn't make xboxhdm 2.1/2.2 because they were bored, they made it because xboxhdm 1.9 had limitations - one of which was the need for 2 separate IDE ports on most motherboards at a time when most new motherboards only had one IDE port.
I suspect that you're just lucky, and yours is one that works with xboxhdm 1.9.

The best
general advice is still to use xboxhdm 2.2 on motherboards with only one IDE port.