Interesting. I recorded it, I'll try and put it through some kind of video program and count the frames. What's weird is that it can break the armor and still escape the throw, which means the throw immunity is during the active window.
I'm just stabbing in the dark here, but my hypothesis is that some of the active frames are counted as recovery frames, seeing as the value for that stat is listed as 0, I don't know what that implies, besides that he is in a recovery state during the active window.
EDIT: OK so I recorded me doing it successfully, as well as me doing it too early and too late. I don't know if it's a just frame, but it's probably not because it wasn't hard to do from blocking Kotal's f1. It works if you stuff his armor at the exact moment that his grab becomes active. This backs up my theory that there are recovery frames during it's active window, though I can't say how much because after slowing down the clips I realized the PS4 recorder is only 30FPS.
Anyone else wanna look into this as well?