I have only seen one place where a flashing taillight would blend in with the background. That was during my stints in Japan where the road department seems to mark every potential obstacle and construction zones with little red flashing lights. This is when I started running steady on red taillights.
In any traffic situation where the cars are running two or more taillights a steady red light would be lost against the background and a flashing taillight is needed.
A flashing light is a better attention gainer, a steady light gives better spatial awareness.
Best to run both, better to run two or more of each.