A few things, actually.
My english is not great, so I'll try my best to answer you, Slade.
You see, as a Leixia player, I hate the fact that I have to guess if the move is gonna hit the oponnent or not after the first hit for the knockdown - especially since it's one of her best tools. It's true that I have to use 66BB to catch backstep, and that's how I've been using for a while, but making it a NC would make things a little better to the player - at least to myself. I can't remember if Xianghua 66BB was a natural combo, thought. There's also another reason: 66B won't break the oponnent guard, but 66BB would. So it won't accidentaly burst if we don't have a bar for the 66BB ~ BE for the 98 dmg.