No, he said Terranort's heart was from the past. I'm now assuming MX kept Terra's heart within the dark realm. Here are the exact questions from the Ultimania (
KHInsider translation):
Nomura: By all rights, Terra should have been revived as himself at that point in time. However, his heart was still in the clutches of Xehanort, and it was unable to go back, and the shell of his body was the only thing that revived. Then, Xehanort brought the heart of Terranort from the past and put it in that shell of a body he once controlled.
—From when was Terra's heart inside the Guardian*?
Nomura: Terra and Xehanort's hearts were eternally struggling against each other within Terranort. This process meant Terra's heart was caught constantly moving back and forth from its original position to the Guardian. By the way, the official name of the Guardian is "the guy behind him" (laughs).
I can see why that last answer can give you the impression that regular Terra is from the past. However, when the Guardian appears to save Ven and Aqua Terranort exclaims (From the ENG script) "How?! You fell to the dark-". I think this shock goes beyond his usual annoyance when Terra was interrupting the possession before. Terra ejects from the Guardian and boots out Xehanort with Sora's help. Afterwards Terra thanks Aqua and Ven for guiding him back. I imagine the Guardian itself isn't a being from the past either, but a dark force that waits to be summoned.
And here's Terra-Xehanort's entry from the table in the Ultimania explaining the Org XIII members (From
Reddit):
Terra-Xehanort | Terra's body containing Terra-Xehanort's heart from the past. | Terra's heart returns to its body, reviving Terra (Terra-Xehanort's heart is eliminated).