I was assuming the receive antenna is also a phased array and the first thing after each element has to be a passband filter and an LNA for reasons of G/T. That

I was assuming the receive antenna is also a phased array and the first thing after each element has to be a passband filter and an LNA for reasons of G/T. That happens before all the demodulation per element. You said the approach was to "overwhelm the receiver to the point it becomes a non-linear device", and pushing that LNA past P1dB will start to do just that. If the LNA remains linear, a countermeasure to the process you're talking about would be for its user to lower the symbol rate and number of carriers per channel to increase the C/N of the desired signal in an effort to punch through the jamming, albeit with less capacity. Having said all that, not sure which of the two effects is at play here.