I’d have to say that for me a body on a slab is necessary to consider somebody “knowing”.
Photos, anecdotal evidence, thermals etc may be enough for belief. But a belief, however strongly held is not “knowing”. Knowing, to me includes a level of certainty that can only come with a body and its examination.
If the gov’t or some part of it doesn’t have a body, then I don’t think it reasonable to expect anyone of any authority to stick their neck out further than the scientific community is willing to, and to actually acknowledge a BF.
Anything short of a body can be explained with the possibility of misidentification, guy in a suit etc. and could lead to massive embarrassment for the gov’t if shown to be such.
Of course, the opportunity to dismiss in that way probably suits the gov’t and its employees fine in the CYA or cover up scenarios you guys mentioned