It's because they're TRYING to be secretive about it Commander.
1. There have been no quotes mentioning Noob Saibot yet because he MAY hold a very important part in the story. You automatically think soulnado = Bi-Han as Sub-Zero, but Scorpion not being separated from Hanzo in the original timeline pretty much confirms they're not different characters.
2. The brothers thing could hint at Bi-Han, but I would say it's much more likely that the younger brother differentiate himself as being different from his brother. Quan knew Bi-Han as Sub-Zero and as Noob Saibot. He has very little experience dealing with Kuai besides Kuai brainlessly serving him. Hence why it's much more likely Kuai would have to differentiate himself from his brother.
3.Kuai was dead and was just serving Quan Chi. Makes sense for Kuai too.
4. Highly coincidental that Kuai said "My soul has been corrupted, now it is cleansed" in MK9 and then also having the exchange with Ermac in MKX. Because his soul is not only cleansed now it is FREE. Coincidentally FREEDOM was a HUGE drive for Kuai Liang's whole character in the original timeline. It was the whole reason he left the Lin Kuei, and the whole reason he fought Sektor. He proved that being FREE was better than being a slave to mechanics.
YOU would be using all of this info in your favor if it was Bi-Han who had all this development. You don't even want the character of Bi-Han commander. You want Kuai Liang and all of his story with Bi-Han's name on it.
1. Hanzo and Bi-Ban weren't created in the same way, hence why Scorpion can't throw another entity out of himself, like Bi-Han can.
2. The brothers thing definitely hints more strongly at Bi-Han as Kuai's soul is the 1 that was last in Quan Chi's possession, not Bi-Han's.
The minute that Bi-Han was resurrected, he CHOSE to serve Quan Chi, until Quan Chi deserted him, when Nightwolf kicked Noob Saibot into the Soulnado.
3. Kuai was Quan Chi's slave, as were the other dead warriors in his control.
You conveniently mistaken "serving" for being a slave.
One is done willingly, the other is not.
There's a HUGE difference between being a glorified butler and a slave.
4. Or it's another hint pointing at the possible Soulnado theory, which you dismiss because it doesn't match your opinion.
Corrupted soul was a big thing that was part of Noob Saibot, but again, let's just forget that and give it to Kuai instead.
Im not fine with a story of Kuai JUST serving Quan Chi. Of course I KNOW he will serve him in the first part of the story, but I don't think Kuai being a slave to Quan for 25 years is exactly compelling. Also, me and you both know the reason he's being brought back from the dead is because people had a SEETHING HATE for cyber Sub-Zero. He wouldn't have to even be Quan's slave if NRS hadn't created that abomination which they thought for some reason would be liked.
Also, that's not just Noob's story though like you are making it out to be. Yeah, he served Quan, but he was just biding his time until Quan ed up to escape his grasp so that he could take the netherrealm for himself. Noob Saibot/Bi-Han could be a good character, but I really do feel like you are fine just giving all of Kuai Liang's shit to him. The scar, the grandmaster, the cryomancer discovery, fighting for the forces of light. All of that sounds like Kuai Liang. Why turn Bi-Han into Kuai Liang?
Seething hate or not, it's a ballzy move on NRS' part that I would have respected more than a Kuai cop-out.
On that note, I also admit that Bi-Han being back would also be a cop-out, but you are in denial of all of the evidence that points in that favor, and automatically apply it to Kuai.
It is Noob's story all over again.
Sub-Zero dies, comes back in a new body, aides Quan Chi in the NetherRealm.
Call it whatever you want, but just because you paint an apple orange doesn't mean that it automatically becomes an orange.