Have you considered that if all three wheels skid, there is no difference in wheel rotation speed and the ABS may not activate?
I believe my "antilock braking system" will not allow my wheels to skid.
If a wheel stops turning or slows significantly faster than another, the brake pressure to that wheel is reduced until it regains rpm.
if all three wheels skid, there is no relative wheel speed or even gearbox output shaft speed, therefore you may find the abs confused think the Spyder is not moving and the wheels will lock up.
For grins, try it with a car first, lock up all the wheels quickly, see if the system releases the brake pressure to all four wheels. Seems unlikely but maybe.
If the wheels on the Spyder will not skid, then the computer is sensing rate of decelleration change of all wheels, and honestly, that could be scary in some situations.