It doesn't follow that all claims supported by circumstantial evidence should be treated alike.
It depends on the evidence.
For example, circumstantial evidence can be sufficient to convict one murderer but not another. It depends on the specific evidence and the specific claims, charges, and/or crime(s).
Either you have a piece/whole thing that is identified as an alien craft or you don’t.
Sightings are a different cat, especially if filmed by a reportedly reliable source, I.E. military aircraft films.
H.G. Wells “War of the Worlds” scared the crap out of many people because it sounded so real on the radio, but it wasn’t.
Even a Fox commentator today confused a fireball (meteor) with a flying saucer. There is no limit on gullibility and con-artists, or dupes and suckers.
Calling P. T. Barnum. You are back in vogue!