And that's one of the mysteries we're not supposed to understand yet on purpose, as stated in the Dream Drop Distance Ultimania.
It's the same as with the chambers of repose and waking, these mysteries are kept vague on purpose for KH III.
A lot of people apparently think so because they don't bother to truly connect the dots and more vague points spread across the series. Today, people apparently need everything delivered on a silver platter and/or can't cope with the fact that in a still ongoing series, widely accepted fan interpretations of vague plot points may become false/irrelevant in the scope of new developments.
Sure, one can make a point about several of these "dots" and hints only present inside the Ultimanias and Final Mixes, that is an issue that can hamper the understanding.
It's meant to be like this:
This isn't a "plothole" but a question left deliberately open.
