Why should we make this assumption?
Good question.
Because this object returned a radar signature on a variety of state-of-the-art sensor systems on the F/A-18's, the E-2 Hawkeye flying overhead, and the USS Nimitz and Aegis-equipped USS Princeton.
1947's flying saucers have become today's flying tic-tacs.
Can visual projections appear on radar ?
Exactly, we may be in the same position as a cat chasing a laser light on the wall. (But then I am still on my first cup of coffee.)
We probably shouldn’t assume anything here but it was mentioned that it was seen tracked on radar. I don’t know exactly what is required for an object to show up on radar.