It's difficult to get away from the space craft aspect of some UFO sightings. In the Phoenix, Arizona case of 1997, hundreds of people including the governor (who first denied then admitted he'd seen the UFO) observed a boomerang shaped, illuminated aerial object many hundreds of yards in size at low altitude. People saw this independently from different locations and perspectives, and in extended detail before it simply disappeared. The intelligence behind the object may have played upon an archetypal expectation of spacecraft to manifest the vision, and the disappearance of something so instantaneously resembles a psychic episode, but boomerang shaped craft are not most peoples' default space ship, and parsimony suggests that at some level it was what it appeared to be.
Similarly in the Rendlesham case, a location I visited to get a feel for the place and satisfy myself regarding the more blatant debunks such as the lighthouse theory, a number of serving military including a senior officer observed a wedge shaped craft that emitted what appeared to be molten metal and sent a Geiger counter into overdrive, as well as leaving an imprint and broken branches. At some level the thing impacted on the physical environment.
That said, there are aspects of the UFO phenomena that seem more like ghosts and apparitions, and aerial objects that appear to be conscious rather than guided. So Vallee's reticence in attribution is reasonable given how few markers we have.