He didn't deny that Terra was feeling and reacting to the future though, just that the actual visions were not something he was seeing and were there for the player. Which can actually fit into this theory quite well, those brief feelings about the future would be momentary feedback if you will. Kind of like a glitch or consequence of this link, some emotions from one of the other cameras/vessel he's linked to just kind of accidentally bled into him. Like when talking and thinking about Vanitas briefly future Vanitas's intent to kill Aqua fed backwards through time into Terra. Which is represented to the player by showing us the moment Vanitas was about to kill Aqua.
There is one hitch in the whole issue though. By the time Terra was having these "visions" he was not yet a vessel or "linked" with Xehanort and/or Luxu.
Otherwise though the whole layout makes very much sense as it would also explain Xehanort's "it was all me" statements in DDD towards Mickey in regards to KH 1 and KH 2. Wherever his "main" essence/consciousness was during the time he was split into Ansem SoD and Xemnas, he could most likely see and possibly sometimes even act through them as he had them on his "monitors" so to speak.
I remember having a conversation with another member about this topic already somewhere last year (and thus I can't find the posts anymore cause the "latest posts" query doesn't go back further than January this year) where we compared Xehanort's main essence either sitting in a metaphorical opera viewing box with binoculars watching what his seeds/vessels are currently doing or him sitting in a sort of "command center" with masses of computers and a monitor + keyboard for every vessel he has.