The public has very little insight into both what is "possible" to achieve by military aircraft, and more importantly in this context, their observational capability.
If the navy says that they spotted an unidentified flying object moving mach X at a distance of Y km, that tells geopolitical adversaries things like "they can monitor our railgun fire under these conditions."
Every piece of information we get from the military that isn't through investigation needs to be taken with a massive grain of salt, since it's always been released under the pretenses of information warfare and the tactical consequences of it being public.
And as an aside, not only does the public have very little insight into what the military and its contractors can do, the military itself has little insight into what other parts of the military are doing. It's entirely possible that one observation from one unit was entirely unaware of another unit doing another thing.