No, no, my statement wasn't directed specifically at you (that's why I didn't quote you) but in general who those for stubbornly hang onto the idea that Xemnas either is actively/heavily influenced by Terra or just a misguided Terra with silver hair based on the ambigious hints that were shown in games before DDD.
There was never an outright implication of any definitive influence of Terra himself.
The accusation that DDD destroyed this "part" of Xemnas is not correct as this "part" of him was always only a theorized/interpreted construct.
The notion you gave that both Ansem SoD and Xemnas had no full knowledge of Master Xehanort's overaching grand scheme is correct as well as the notion that they both did act on their own ambition and will to seek out Kingdom Hearts (or rather forcibly build an imperfect artificial one which Ansem SoD did with World hearts and Xemnas with human hearts), but it remains also fact that subconsiously they were still acting on Xehanort's own ambitions and end goals even if they didn't knew the whole plan.
And this is the accusation that can be reasonably leveled at DDD as it practically changed the roles of both Ansem SoD and Xemnas from being respective main villains/antagonists of their own schemes in KH 1 and KH 2 to being a sort of indirect "Enforcer"/General/extension of Master Xehanort whos consciousness sits somewhere in the background and subtly guides both Ansem SoDs and Xemnas' actions.
Even after Young Xehanort "picks them up" they won't know the whole plan as the moment they return to their proper time, the memories of the present (DDD) are erased from their mind.
Ah, good. Sorry about that- I just recognized that I did kind of leave that interpretation open. I agree with that sentiment: while it's true that Xemnas does
kind of recall some of Terra's memories and refers to Aqua's armor and at one point a comatose Roxas as 'friends', as well as there being enough of Terra in Ansem there for Riku to be reminded of him in 3D... That's not really enough to suggest that Terra's influence was enough to do anything other than delay Xehanort's plans take long enough for Ansem and Xemnas to be destroyed by Sora.
Yeah, I was aware Ansem and Xemnas lose their memories of the present after they're eventually sent back to their proper places in time. Of course, that doesn't stop them from acting like they knew what they were doing the whole time during their time in the present. That still doesn't explain how they knew what roles they had to fulfill- Xemnas is one thing since Braig/Xigbar was their to guide them, but how did Ansem SoD know to go back to the past? That's very clearly the
only clear thing Ansem knew he had to do, but the rest of his actions suggest that he was the most in-the-dark of the two. 3D offered zero answers to that...
...The Re:Coded Secret Ending from 2.5, however, might have implied one. Young Xehanort states that Master Xehanort's Keyblade carries a will that is passed on. That will would explain a lot of the gaping plot holes 3D left- especially if that will is embodied by the Guardian Ansem always has at hand. Whenever Apprentice Xehanort needed a little "push", Xehanort's Keyblade/the Guardian provided it. Since Xehanort's Keyblade is likely connected to the sixth Foreteller, though, 3D wasn't able to touch on that since it would carry some [chi] spoilers that weren't anywhere close to being revealed when 3D came out. That's my theory, anyway.