It only stays on DL+IOG if you are close enough to the ground. If you are a few thousand feet up, the missile will be higher than you, but it’s still able to track you without enabling the PD filter, so you can enter the notch angle and it will turn off its PD filter instead of going to DL+IOG. It only relies on datalink when you are less than a couple hundred feet above the ground.
In my experience its just not reliable even at altitudes. The missile will often reacquire again if you leave the notch, so it ends up being just a waste of time and chaff trying to notch it early.