I'm not sure if you guys are familiar with instant replay or if you have ever been hit in the face, but...
1. when you get hit in the face, it takes a second to kick in. With a lot of other "flops," you get hit in the body and your momentum is already taking you down, so it looks smooth. When you get hit in the face your immediate reaction isn't to fall over. When the pain/feeling kicks in is when you flinch and move backwards.
2. Slo-mo instant replay kind of... uh... slows things down. So when it takes two seconds on instant replay for Monte to flinch, it didn't actually take two seconds in real life for him to flinch...