“He said that speculation on UFOs was encouraged as a cover for US military testing. That might be why so many of these things are sighted in the US Mountain Time Zone.”
Many of the most famous cases are in the US Mountain Time Zone but if you dig a little deeper you will quickly see that the phenomenon is everywhere in the US and around the world.
That said, your first statement is correct.
So, the trick is to separate the truly unexplained phenomena from the noise. I had heard that some serious equipment was used to check Loch Ness for Nessie, and the results were negative. That was a relatively easy one because the phenomenon was localized. Some still believe that she was there, but had died. A little trickier to check the whole wide world.