Hmm. I'm not sure if I understand the connection between these two sentences:
"During the revival, what happened to Terra's body, and Terra's heart that was in opposition to Xehanort's control?"
"In Kingdom Hearts, Birth by Sleep, it is to be considered that it was thought the whereabouts of the heart of Terra's master, Eraqus rested within his body."
To me, they seem detached. If I have to draw a link, that would be something like this: it's because of the presence of Eraqus' heart that caused Terranort to split into Terra and MX upon his revival after Ansem SoD and Xemnas had been defeated. I might be wrong, though... if I am, I'd very much appreciate clarification regarding this matter.
Anyway, if it's already explained as such in the Ultimania, I guess there's nothing we can do but wait and speculate further. At least we know that this is by no means an oversight that might have led to a plot hole.
detached because they do not belong so close together. The first sentence only gives out the questions to speculate about while the second reminds the audience that it was hinted in Birth By Sleep that Eraqus' Heart rests within Terra's.
If anything, it's a hint in Nomura's typical vague speech patterns that Eraqus' heart may have something to do with the mess, which is actually something he preached ever since the BBS secret ending Blank Points was officially released.
Nomura keeps on reminding the audience about Eraqus' heart being in Terra and that it may be important later, but he doesn't reveal any further information on this.
Unlike the Sora/Ventus/Roxas-connection, which is pretty clear and explored throughout the series, the whole Xehanort/Terra/Eraqus-mess is kept under wraps on purpose while constantly being teased about.
Since we do not know
if MX and Terra even split at all, we can set that only as speculation as well, but that is actually what Nomura wants
There is no clarfication on the matter, also in regards to Eraqus and why MX came back because Nomura does not want a clarfication on this (yet).
Yep, it's indeed not a plothole, in fact, many of the points some people designate as plotholes throughout the series are not even really plotholes at all.
There might be something on timeline between the end of KH2 and the end of DDD , I mean when Xemans was defeated,Terranort was supposed to be back right away , since Ansem SOD has been defeated a long time ago before Xemans.
So maybe between that time when Xemans defeated(end of KH2 //Terranort should be back) untill MX appearnace in the room where nothing gathers(DDD End // a long time after KH2 ending) Something happend and Terra somehow managed to get Xehanort out of his heart/body , and when MX showed up it was after Terra got him out of his body.
We do not know how long the revival of the original persona takes after both Heartless and Nobody are destroyed, so to say that Terra-Xehanort should be back "right away" cannot be confirmed. It could even be thathe period of time needed for the revival is different for every being.
Then there is not to forget that Xehanort is a special case in every possible direction, so what exactly happened is murky.
It is however highly possible that due to some circumstances Terra's body may be no longer Master Xehanort's main host, even if it is still used as one of the thirteen vessels, either controlled by a shard of MX's heart or possibly even the newly grown heart of Xemnas.
There is no "long time" after the KH 2 ending though, as Re: Coded takes place directly after KH 2 and takes only a few days, and between KH 2 and DDD less than a year has passed.