Doesn't it strike you as odd...
...that the same sinister government conspiracy that is so successful at covering up these sightings is incapable of preventing you from hearing about them from 13 celebrity astronauts?
If even one of those alleged reports actually had any substance to it, the space program would look very different than it does now. Every spacecraft and space station we and every other nation operated would be armed to the teeth, and there would be a Planetary Defense budget of several hundred Gigabucks passed by Congress every year.
As one other famous astronaut once put it:
"Military secrets are the most fleeting of all."
LCDR Spock (UFPSF)