Aye, that's part of the "saddest days in EBO history" :P
Are you freaking kidding me? Do you remember how lopsided the battles were between the otherwise rather comparable Brihentin and Hippeis Xystophoroi? How the Azad cataphract unit was made utterly unplayable except against barbarians by armor-piercing kopides? How in general cataphracts were considered rather useless before this change (if I recall correctly)?

AND it makes no sense for the thing to have AP.