Some ABS systems pulse the whole system all at once if one tire locks up.
Others pulse each wheel individually. I am a HUGE fan of the individual pulsing.
There is absolutely NO point in pulsing all the wheels if they are not all locked up. My car pulses each wheel individually so I can still have normal brakes when the ABS is working, depending on how many wheels are being pulsed. The truck is another matter. You have to be very careful how hard you touch the brakes as it will very easily lock up all four on dry pavement!
If driving bare foot, my big toe can put an unsuspecting passenger through the windshield
....if they were not wearing the mandatory seat belt. I pretty much have to down shift to slow down on snow/ice without sliding.