No problem.
It is the general rule though so it doesn't apply only to Xehanort, although one may argue that it is normally not a thing anyone would try because it requires getting turned into Heartless or actively transferring your own heart to "shed and store" your body.
Only true Keyblade Masters have the ability to extract and transfer their own or others hearts though, as Xehanort himself states in the BBS Report, so the ones who could actively exploit this mechanism are rather few when in comparison with the whole populace of the universe itself.
Xehanort is all-and-around a special case anyways and ever since BBS he has been built up more and more as someone who's almost a "villain sue" as some may say.
I'm personally more frustrated with the fact that such clarifications exist but are largely inaccessible to large parts of the fanbase due to not being in the main medium.
Have fun rummaging through it, chances are you'll find some vague foreshadowing stuff mentioned that has been clarified or expanded by some of the later games.
While Nomura admitted that he is only ever planning one game ahead in detail (i.e. he was planning BBS while making KH 2) it was around the time of KH 2 FM (when this report was also made) that he started to set down a full general conceptual framework of the whole saga.
If you're interested in meta-knowledge in general, the main site also has an interview-section for every game with translated Nomura-interviews in the Ultimania books and several game magazines.
The Ultimania ones and some of the Famitsu interviews are especially important when one looks for clarifications on story/narrative-related issues. The explanation as to why Vanitas has Sora's overal appearance for example also comes from one of those.
