If you're going to call his use of those terms incorrect, can you explain a craft travelling supersonic without jets or rockets, leaving no emissions, utilizing no airfoils, consistent with our understanding of physics?
but more generally, what he's saying is that the sensors are not infallible, especially when dealing with advanced materials.
As to actually meeting your given qualifications and assuming the sensors were right and told EXACTLY what you specify, no I can't. But I can't explain that even when including QM and nuclear tech (or rather what I can even fathom by stretching well into the realms of almost possible). Even things like EM drives or anti-gravity should leave other types of signatures. (Note: I do have a physics degree. I also studied exotic propulsion devices.)
I'm going with Occam's Razor here and guessing at advanced stealth tech or simply the system failing.
Separately, radar operators saw something they didn't understand. It could have been noise as they are now looking out for tiny drones and very small radar signatures, they have sensitivity turned way up. Sometimes you see things that aren't really there.
I'm honestly going weather balloons on this one.
That’s because you’re watching a YouTube video that was filmed on a potato, instead of actually, y’know, being there.