Along with not doubling 9 vs. 3, it's one of those plays that costs you absolutely nothing, and also is the max EV play, and makes you look like an unskilled player to an observer who doesn't know the indices.
I play 6 deck, S17, and I have slotted it in at TC-3 (together with 13v3 hit, and A3v5 hit - all the threes). With min bet out at minus counts, I can't think the H17 index will be any different?