In the Type 2 spec there is an additional resistor on the control pins of the cord that communicate the current capacity of the cord to the car. That, along with the signaled capacity of the station gives the car the maximum current it can draw.
Interesting, I wonder if resistor-coded detachable cables could be retrofitted into J1772 or NACS without breaking compatibility. As long as it's possible, it'll probably happen eventually.
https://en.wikipedia.org/wiki/Type_2_connector