Do Apple's USB-C power adapters execute any code?

Technically, all USB devices are smart with their own micro-controller.

Older USB devices did offer direct power services for older cellphone and like devices. USB-C also offers this as well for low end devices.

Modern cellphones and computers that offer quick charge technology need to communicate with the charger. Apple's older MagSafe was such a charger setup using the one-wire comm link between the system and charger. Apple's USB-C charger is no different.

I would recommend you review the USB-C spec (you need join to get to the docs) as well as Qualcomm Quick Charge spec If you are trying to build your own charger. You'll also need access to the Apple Developer - Hardware.

Also keep in mind there is two different specs for USB-C type of connections!! The USB-C with the USB logo and then there is the Thunderbolt 3 (USB-C) with the lightning bolt: Adapters for the Thunderbolt 3 (USB-C) or USB-C port on your Mac

And yes your Mac & charger communicates between them.