It's late and I'm tired...please enlighten me.
That it doesn’t matter if demons or fairies are real, but the phenomenon of contacting them is the same or related to the supposed contact with aliens.
You dismissed the observation because the observer, Vallee, believes literally in it as supernatural, but his belief in that doesn’t discount the accuracy of the observation.
Demons and fairies are by definition supernatural. But theoretically and ostensibly UFOs and aliens are not supernatural. So understanding UFO alien belief is actually just another variation of these age-old beliefs is an important observation.