Wilwood and the Spindle confusion

The two kits, 140-11019 and 140-15465, are identical in every way except for the 1 part-->The caliper bracket.
Both kits use the same Hub, Rotor, Caliper and hardware.

Which is curious because the MF spindle and Stock spindle can use the same Stock Caliper no problem but for some reason those two spindles can't mount the same Wilwood caliper.