I checked my C5 installation and I to could not find that patch.
If fact there are a lot o’ missing HAO patches.
When I first installed C5 HAO worked fine for me (especially for drums) but I seem to remember
that when C6 came out (with Halion Sonic SE), my HAO plug got a lil funky.
I may be wrong but I believe it was a 32 vs 64 bit thangy.
But if you are still using C5 or earlier, you should not have this prob.