Speaking of "disinformation," I encourage you to research the origin of two sayings which became very popular in the 1950s: "flying saucers" and "little green men."
Also, the source you cited is, to put it mildly, questionable.
Goode's book is heavily supported by official documents obtained via FOIA and has nearly a thousand footnotes. It mostly covers the level of secrecy this matter was held at, and how astronomers, pilots, sailors, military personnel, and law enforcement officers who officially reported such sightings were strongly urged never to speak of it again, and if they went to the media their career was over and they were accused of psychosis. That was kind of a thing for half a century. My grandfather was a dirgable pilot during WW2, patrolling the Bermuda Triangle for U-boats. He and his copilot were told, off the record, by their commanding officer that if they ever saw anything like that never to put it in a report or put it out over the radio.
Vallee's book explores corrolaries between Hynek's "encounters of the third kind" and similar cross cultural legends and folklore. It's an interesting read.
Our top scientists only have a very generalized idea of what these things are, but as they are no longer deemed a clear and present danger to national security, they are largely ignored. None of our weapons have any notable effect on them, and they can fly directly into the ocean or the side of a mountain at Mach 2 without leaving a trace. I think they're cool, but after researching them for over three decades don't really think about them anymore. It's best not to overthink some things.