It will frequency hop almost at random 40+ times per second, and no jammer is going to be able to flood the sky with several MW of radar energy in each frequency slot across that whole spectrum simultaneously. In at least some frequencies the radar will hop to, the radar will illuminate the target's area of sky with a huge amount of energy against a zero background, and only the target will reflect an appreciable amount of that energy back. Huge signal plus very low noise equals massive advantage in detection range over the best possible IRST.
I agree with your conclusions, but the APG-77 hops freqs at >1000 per second, making it very difficult to jam. This is also one of the reasons why it works well for LPI too.