I think they believed that the phenomena as a whole may represent a number of different ‘things’.
It doesn’t strike me that Vallee believed it was all ‘evil spiritual entities’ if he would say, “I’ll be disappointed if UFOs turn out to be only spacecraft from outer space.”
I think he was interested in how study and attempting to understand all of this might inform our as yet paltry grasp of the real natures of time and space.
We tend to read that a bit differently. We think he meant that if it all turned out to be simple tangible craft etc. etc. etc. then it would not be as complex and interesting as he'd so far observed, researched it to be.
Our reading of Dr Vallee's 3? books depicted Vallee's perspective as fairly consistent across all of his books. He meticulously and tediously to the point of almost boredom documented how the ET/UFO stuff rather shockingly closely paralleled poltergeist and other dark occult goings on in the night through the centuries.
It did not seem to us that his perspective was all that diverse, at the point of his writing those books.