I think we are talking about “angels” and “demons” and the Irish “fairies” and “leprechauns” and other strange “beings” who appear here and there to all cultures throughout history and in myths and legends.
Like ants looking at humans, we are not really processing what we are looking at....so we build models to explain it but they are all just models to make us think we sorta understand it...
This is a really cool series of books showing the wide variety of stuff we are dealing with:
https://www.amazon.com/Humanoid-Encounters-AD-1899-Others-amongst/dp/1542722055
So—my issue with Elizondo (and folks like him) is that they are so culture-bound (.gov,.mil etc) that they totally miss the big picture.
It is like looking at the world through a keyhole—when all you have to is open the door to get a better look...
On the other hand, they just maybe tourists, vacationers and a few Special Circumstance folks thrown in for good measure. There are many humanoid species in the Culture which would account for all the different body shapes and odd behaviors. They just wanna have fun!