I don't mean to keep prodding you (trust me, not my intention!) but I am genuinely curious. How did you get that impression? In my 15 years of playing these games I never got that impression at all. I'm actually keen to discover if there's anything I'm missing. Why would the game make pointed and repeated references to the True Sith only for them to be irrelevant/be superseded by a different enemy? That's what doesn't make sense to me.
You're right, a lot of what is said is deliberately vague. Nevertheless, these references are why the only impression I ever got was that the ultimate enemy was the True Sith:
"She said that the teachings here (Malachor) will lead one to the Sith...the True Sith...and all of their shadowed worlds."
"It because Malachor, like Korriban, is on the fringes of the ancient Sith Empire, where the Sith wait for us, in the dark."
"It (Korriban), like Malachor, brushes the edges of the Empire that waits in the dark. And like Malachor, the Sith have forgotten it...for a time. They will remember. Revan knew this."
Yes, none of this is tantamount to a direct admission. Still, given all these references, I don't think the situation is as open to interpretation as you suggest.
Yes, they do. In vanilla actually.
"You are wrong. The Sith is a belief. And its empire, the True Sith Empire rules elsewhere. And Revan knew that the true war was not against the Republic. It waits for us beyond the Outer Rim. And he has gone to fight it in his own way."
"Even the small one - who waits for you outside this place - I sense it has one last journey for you. You must go where Revan did into the Unknown Regions, where the Sith, the True Sith, wait in the dark for the great war that comes."
I get where you're coming from, I really do. I just think that trying to draw any other conclusion is very much straw-grasping. Sorry to keep posting but having put my thoughts out there, I feel perhaps duty-bound to defend them.