Actually, there is MORE then that going on here, and probably every club you have ever been unless you are living in the suburbs.

The girl with the security jacket is checking IDs and collecting cover. She is wearing a security jacket so it's clear she's a employee if she's standing outside the door. She is also wearing it so she looks like the clubs security. A little bit of deterrent for would be light troublemakers (shit I remember seeing a security jacket/shit that place always has security), but also because she is a SHE. In the case of a major security threat, she is less likely to be a direct target of an attack to subdue security. That being said, she is OBVIOUSLY NOT security. How could you be security for a club when you have to stand outside the door/inside in one place all day, constantly distracted by looking at IDs/taking money? What happens when something goes down, you throw all the money on the floor and go take care of it?

Notice how the bouncer is just sitting down, chilling, in regular clothes? Yeah, that's the real "security". Regulars all know him, and feel safe that he's there. When they get drunk and want to fight, they think twice. Non-regulars (the ones most likely to try and rob the place) don't know the set up. So the see the girl checking IDs and taking cover charges and think she's security. They don't think she's that big of a threat when they look at her from a distance, and when they get close enough, she bolts (like both instinct and her boss tells her to do) and they don't perceive her as a threat at all now. This is extremely important. It keeps "security" from getting shot or stabbed before they even know what's going down, and also gives the real security a heads up that danger is in coming.

Notice how the bouncer is around the corner? He didn't get there by accident. He is in a position to watch who is coming in but be able to get out of line of sight and force them to come around a blind corner at him if he's spotted. Like most bouncers, he's a damn tank, slow as shit but if you get within range of him you are 10 kinds of fucked.

None of this is some massive psychological read. This is standard tricks of the trade for people running places like this. Security has been around for a long, long time. It has had a lot of chances to evolve and adapt. If you going to open a club or a bar and you plan on having a bouncer, unless you are in the suburbs you don't just "hire the biggest black buy you can find" and then plant him in front of your building. If there is a real threat of a real crime, all you are doing is going "SHOOT THIS FUCKER FIRST and you can have what you want!".