CS6 simply doesn't have the required code and it cannot be added.
Correction: CS6 simply doesn't have the required code, and Adobe simply decided not to fix that, as they would simply prefer we purchase Creative Cloud, and simply shell-out $50 every month, because that just quite simply makes the most sense to them.
You can believe what you like, but it won't change the truth.
CS6 is a Cocoa application, and Retina support requires Carbon (or the other way around, I'm a Windows user). It's not a matter of adding a few lines of code to make the change, it required rewriting the entire program from the ground up.