My concern would be that physical asymmetries in missile shape, weight distribution, fuel burn pattern and the like would distort a simple ballistic trajectory, and cause a backward trace based on a few path points to indicate an erroneous launch point.
Maybe I'm wrong.
weight distribution doesnt do much. Thing flys like a sock with sand in the toe. If your radar paints are close to the launch point, there is not much error at all. If your radar paints are at the impact end of the flight path, you do get error from wind.
Katyushas are simple, solid rockets with fins. The fins are not on quite straight, so they rotate a bit to spread the error on all sides of the aim point. Straight ballistics is a pretty good match. It is not much more advanced than the Hale's or Congreve's rockets of 150 years ago.
You can program in a dogleg (down range turn) into US ATMS, but that is a guided missile.
Israel is a world pioneer in unmanned aircraft and remote sensors. They probably have them overhead, and the flash of a katyusha is visible from several counties away.
The big weakness of going after the launchers as a tactic is you can launch a katyusa with a frame about as complex as a set of bedsprings. The guy launching it can set it up, run a wire a few buildings away, and press the button from there. That is why it is particularly onerous that the rockets are launched from civilian houses or courtyards. The actual launch button can be in any of the surrounding houses.