Only Nomura said that he probably didn't flip through every single page, because people brought up the exact same issue to him.
So that point if kind of nulled.
I wouldn't put it beyond Namine messing up with the journal (albeit hardly from the same reasons DD does) but we did see before the journal can be messed with by whatever means they used in the first place.
If anything, I'd kind of like for it to have been Xion that put it in, seeing how she has a high possibility of being part of what connects all three games.
