As noted, the words 'ghost', 'spectre', and 'wraith' all mean pretty much the same thing in any non-D&D context. Therefore, this is an area where they basically have to go look at the old edition descriptions of the three, and describe them accordingly.
Without being able to reference my books, I would say that Klaus had it about right.
Edit: the other option, of course, is to do as GX.Sigma alluded, and have one monster that can be skinned a hundred and one different ways, thus covering the wide range of ghosts, spectres, wraiths, bogeys, apparitions, eidolons, and the like that exist out there. And thus, any given ghost can be more or less aware, more or less motivated by various things, and have various different powers. But I wouldn't expect WotC to go with that - in general, it's easier to use a toolbox of 20 subtly different but 'complete' monsters rather than a single multi-function monster that needs assembled first (as with the 3e Dragons).