Sparring flat knacker changes the game in that you cant react as much as you need to preempt. Someone puts a rush on you and you have eaten four shots before you can get a simple defence like hands up. Let alone a complicated one.
Supprise adds even more to that reaction time.
This is one of the usable differences between street and sport.
So here is a takedown that does not work. One handed arms free. you can do anything and everything to defend it.
Exept it was done quickly.
This kind of gells with my experiences. Where i have seen guys dumped and done little more than flail in the 2 seconds it takes to gain a dominant position.
Now imagine that was a knife. the police officer is at risk for 2 seconds. And then at less risk.
If I grab the arm I may be at risk for 3 seconds which is more time for me to get stabbed.
Now there are of course circumstances where one works and one doesn't. But those who suggest that one always works and one doesn't do not understand the mechanics of real world fighting.
This is one way of testing the grounding someone has in real world fighting.