Thanks for explaining. To somebody who just types 'latex' at the command line (Tex Live behind it) the different possibilities you mention are too complicated.
My point was, it TeX in Moodle Docs were identical to TeX in moodle.org, the life of some of those (unmotivated) volunteers would be more pleasant.
Or to put it another way, it is easier and nicer to document a document processing system from within itself!