few things to note here.
This is real IMO.
I trained in a good gym before, and had some people who fought on local promotions.
During their training, they put ALL of us non-pros trying to attack them.
The rules: They can't attack.
Seems easy, right? WRONG!
These guys would go through all our class and almost never get punched clean in the face.
It is VERY hard to hit someone who knows how to defend himself and is ONLY doing that.
If you fake and they attack, they open up.
If they attack, they open up.
A guy who's only defending does not open up, and as such, it is hard to punch them.
Take an UFC pro, and I am sure they can see your punches from a mile away and either block, bob and weave or get out of the way easily.