I had read many years ago in a old book where Israel used it to make Iraq think Israeli planes (which was in close formation) looked like a 737 or 747 (forgot which one)passenger plane. Thus they weren’t considered enemy aircraft.
I see.
That is a common myth that makes the rounds now and then.
Flying close together may help in some targeting situations, but not much, really.
Flying in the radar “shadow” of an airliner may be possible but it would require detailed and extensive awareness of the beam and its shadow (changing all the time).