UFO crash retrieval appears to be absolutely real

That argument further supports the idea that there's no reason to keep alien artifacts secret, making the entire notion even more implausible.

Without evidence I do lean toward Grusch either being a grifter or mentally ill (possibly some combination)...but even if nothing could be reversed engineered there would be very good reasons to keep it a secret. [Consider the religious foundation of many nations, and how knowledge of alien craft could be destabilizing for example.]

However, given the lack of evidence, I think we can just say there isn't a clear reason to accept the US gov't has alien tech from downed aircraft at this time.