In a simulation where the only radar reflector is one simulated jet, and there is no real hardware, it’s pretty easy to hit since the Pfa is effectively zero. In the real world, there’s a thousand different things which will give some similar energy return and there’s no simple way to filter that out without actually seeing the thing in real life.

Stealth isn’t about zeroing the energy, it’s about pushing it into an ambiguous state space where it cannot be distinguished from birds and shit.