Yea, very possible indeed I think that's a good explanation.

I wouldn't normally discount what I had read elsewhere, except that I usually fly HKG-PEK 3-4x monthly (as well as sometimes booking CX flight #s on KA metal to a number of other cities in mainland China, mainly being PVG and HGH) and have had gotten an op-up in this situation quite a few times. So maybe CX/KA are different from other airlines I suppose, sounds like at least different from QF or JL. I still can't say authoritatively though if it doesn't negatively (or positively, for that matter) affect my op-up chances, because I guess CX/KA only knows that. However, anecdotally from quite a few flights I do know I have gotten op-upped when I was on the CX codeshare # for a KA flight, and vice versa.