Theortical Situation - Safe Jumping a Landed Jump

Would it be possible to “safe jump” somebody that is landing? I’ll make up a theoretical situation. Pretend it’s Yun Vs Seth. Yun divekicks, Seth jumps over, and Yun immediately divekicks Seth while he’s landing. But, seth has only empty jumped forward. So from there, he has those “2 frames” of landing time that you are apparently suppose to have if you don’t input any attack within your jump. In those two frames, would Seth be completely vulnerable and would be unable to DP yun?

No, you are able to block during those 2 frames.

Are you talking about Trip Guard?