You had to wait for the vanilla marian reforms to get cataphracts as AS in v0.8x. You must have just been lucky and gotten the reforms earlier then your upgrade to your barracks.

Even though cataphracts are listed on the recruitment list, they cannot be recruited once you complete the MIC. A trick is used so that you won't have to upgrade your MICs after the reforms as you have to do with the Romans or Celts. (Thanks to FATW helping us with this trick!)