It is confusing if you're not used to it. The Oklahoma Youth Expo (OYE) and the Tulsa State Fair (TSF) have always pretty much left it up to each state breed association to make their own rules and do their own classifying. When the associations were requiring registered pb's, both the Angus and Hereford breeds were getting so small that they were about to disappear. This probably has alot to do with the way sale order is chosen - both of our bigger shows only sell 60 - 70 steers total, and whatever percentage of total steers in the show that a breed makes up is equal to the percentage of steers it gets in the sale (if 5% of the steers in the show are Angus, then 5% of the steers in the sale will be Angus, so if 60 total get in the sale, that's 3 Angus steers). OYE rules state that a breed must have at least 15 head to qualify both champion and reserve for the premium sale, 10 - 14 qualifies only the champion, less than 10 and the champion and reserve compete with all other breeds with less than 10 for 2 sale slots as champion and reserve AOB. Some counties do it by percentages, others show for sale order so you either need numbers or you have to be able to compete with the crosses, or else people will just choose to feed a crossbred steer to begin with, because there'll be alot more of them in the sale.
So basically the requirements for the breeds in question are;
Angus - Must be solid black (no white in front of sheath), polled, and out of a registered Angus cow.
Hereford - Must be Hereford in appearance (color and markings) and body type.
Shorthorn- Must be Shorthorn in color and type. No blacks or blues allowed.
I look for OYE to go to a strictly visual classifying system eventually, like it's done at the TX majors.