not necessarily so
even head-on there's probability it would keep going
and when I engage them from very close range from the rear in a stealthy way (radar off), so they don't pop flares, chances of a one-shot kill are pretty high too ...
my observation is - chances of one-shot kills are much higher during very close stealthy attacks from any aspect, so they don't maneuver too much or pop flares
but, for example, if you're chasing an eagle, which is going extremely fast on an afterburner - even if you're close on his six with radar off and he just keeps flying straight, accelerating, not even popping flares, your magics might not have enough energy to take him down with one shot... they'll detonate half a meter behind him ...