If David Grusch had showed up with a bunch of family members who claimed to have seen UAPs being dismantled with their "spiritual eyes", then perhaps I'd put his testimony on par with Joseph Smith (and Oliver Cowdrey and David Whitmer)
Of course, I would expect some internal investigation into if and why he is claiming these things, if it's not already known. But I don't see why anyone should spend any significant resources (let alone the public at large) going by the words of someone who is payed to hide things from the public.
If there is a conspiracy inside the DoD to hide reverse-engineering projects from congressional oversight, as Grusch claims, then there is a good chance that no investigations will actually be performed without significant pressure from the public.
That is why public engagement is important. Public apathy enables corruption.
https://archive.ph/RsStS