It's interesting to note some of the odd things that turn up in a careful reading of the Monster Manual. Remember that this was the first of the AD&D books to be written, and some curious textual artifacts are still contained within it.
For example, in describing the Wand of Orcus, the Monster Manual states, "Other powers of this device as rumored amongst mortals are dealt with in another book." Could it be that the title of the Dungeon Masters Guide was not yet firmly established when the Monster Manual went to press? Impossible, as it was mentioned elsewhere. Did this just fall through the cracks?
Another, when describing the many and varied powers of the demon prince Yeenoghu; "magic missile (3/day, 6 missiles/cast), each doing 2-8 points of damage and having a +2 to hit;". +2 to hit? For a magic missile? Again, is it possible that the property of the magic missile to always hit its target was not yet firmly established?
There are many others, of course; spell names that are subtly different (detect invisible objects or detect invisible, as opposed to detect invisibility, etc.). Some are simply curious names that are never really explained, although I can, I think, figure out what raise dead fully does.
None of this detracts from my love of the original, of course; quite the opposite. It's interesting to remember that there was a time when Advanced Dungeons and Dragons was still not yet fully published, and I like the fact that even one of its core books reflects upon the whole as a work in progress.