I see we spent a good portion of this thread going over stuff again (Zombie emotions and whatnot) so let me add old info to the discussion.

The first indicator that they weren't normal came during the incursion after the introduction of Pegs. One creature hid from them.
The second was after Burt's rescue with the infected sleeping.

We already knew Pinstripe could read and thereby.. reason. He also displayed "fear" or maybe caution when he got into tower II and was playing dead until he found out they were out of ammo. He was going to attack until Bruh Saul whipped out his "Knife". He reversed course after eyeball'n that.

We had the reaction or lack of a reaction to Datu falling into the trap. He was captured, not killed.

The infected taking one person at a time and clearly picking who went and who stayed in the room

The Behemoths even show a level of reasoning from the Kalani/Angel/Skittles episodes.

Someone correct me, but I also remember hearing Mr. Suit chuckle after he caught Riley's arrow.

Ok, enough on that topic.

CJ.. CJ... CJ...
Her little hiding spot wasn't a Bug out bag. That was a weapons stash that only she knew about. She didn't even trust Shawn to know about it. Her paranoia cost them the tower. Piss Poor weapons storage cost them lives.

At first glance, it would seem like it was everyone for themselves (more so in CJ's case), but when you look at the rescue attempt (which is slightly puzzling..more on that later) you see a coordinated effort.

The "Rescue Attempt"
Who was leading it?? Did it not work because there was no leader? maybe it was Angel's poor leadership? Joking, joking...

CJ is holed up in the basement and Shawn and Hope are presumbably stumbling their way south about now, so it wasn't either of them.

My opinon on why CJ was left alone:
Simple reasoning. Risk vs Reward. They had enough people and she was in a defensible postion with an unknown quantity of ammo/weapons and showed the skill to use them.

I also think Duncan/Skittles was left alone simply as a "Ah Haa!"
Like a sick pat on the back.. a perverted "at'ta boy", thanks for letting us in.... now watch this!