It is milliseconds between it being a completed takedown and a late hit.
What I don't like is that first, Winston was still fighting to stay up....he was NOT down....and second Tree hit him shoulder to shoulder. I heard no whistle and no claim that the whistle had been blown thus ending the play. Yes, it was a tough hit. But hardly a cheap shot or a late hit. Isn't this what football is about? All Winston had to do was quit fighting.
I'm not upset at the officials, however; they are told to protect the QB and they are going to give the benefit of the doubt to the QB.
But players have to play and if the ref blows the call, so be it. Basically, what has changed is that there are simply more penalty calls when sacking the QB than there used to be.