That is not true. Existing technology can take out remote controlled conventional drones with EW.

I know of no existing (human proximity safe) EW that can handle optical based or internal (IMU) inertial autonomous flight, and both of those are more than good enough in this scenario (though optical may limit the upper speed bounds depending on the onboard processing capabilities). IMU based (pre programmed) could easily allow no active sensor mode, though would require pre-scouting the route.