The cable has a few wires dedicated to directionality (CC1 & CC2) lines as well as sideband channels. My guess would be that the first device to be plugged in s

The cable has a few wires dedicated to directionality (CC1 & CC2) lines as well as sideband channels. My guess would be that the first device to be plugged in sees nothing on the other side, decides it's going to ask for power, and configures itself (and thus the cable) as such. The second device sees a USB-PD device requesting power and begins to provide it. While I don't doubt the foresight of Apple HW engineers, the possibility strikes me that this is entirely accidental and derived from the design of the USBPD spec. If so, these "stars align (but only because the spec was functionally designed)" moments are some of my favorites.