I happen to have almost all of his ufology books including "Passport to Magonia" and you're right that he covers those subjects, but he doesn't claim it's a collective psyche phenomenon. Instead he argues that it has elements of this but guided by an external control system, which is itself part of some, for lack of a better word coming to my mind right now, extradimensional intelligence (he never makes this specific word use) that manipulates human beliefs by manifesting entities in a way that corresponds with the more general belief tendencies of any era. Thus, in ancient times, what we now call UFOs manifested as "fairy folk" and such while today the tendency is more towards temporarily physical apparitions that are made up to be "aliens", presumably because it fits better with the psychological tendencies of our current technological, space-exploring civilization. His core point though is that in both cases, we're really seeing the same extremely ancient phenomenon recur in different guises. Many nuts and bolts UFOlogists really dug into Vallee's ideas because of this, but to me at least, it actually makes a lot more sense than UFO's being aliens in the classical Hollywood, scifi sense of the word. Their behavior makes no discernible sense in that context.