mmm, I tend to remember from the 757 and a300 course that these aircraft DID use aircraft groundspeed. The anti-skid computer is the main thing in the system. It gets 8 input signals from all the main wheels. This signal is detected by a 30-40cm long probe in the center of the wheel axle, and the probe measures the wheel speed in revolutions per time frame. The anti skid computer calculates this into velocity. A 9th signal that goes into the computer is aircraft ground speed (from GPS, INS, computer...). When wheel speed is slower than ground speed, that means this wheel is skidding. Then the computer sends a signal to an anti skid valve that shuts off hydraulic supply to the brake/wheel skidding, even when the pilot presses the brakes. When wheel speed is the same as ground speed again, braking is normal.
That's how I learned it, if you say it doesn't use INS you can be totaly right.