I haven’t done the math to see what equivalencies are, but:
The “oat flour” that Succeed uses isn’t just oats ground to flour. That’s still the whole oat, just in a different form, with all the starch it brings.
Succeed uses oat bran, not the whole oat, which is where a large part of beta glucan lives (also in the endosperm), to make the “oat flour”, so every X amount of this “oat flour” has a much higher % of beta glucan, and hugely lower amount of starch (if any)
Succeed also uses oats with more bran, therefore more bg, than the average oat
Oat Flour in SUCCEED: All About The Beta Glucan Concentration (succeed-equine.com)
So while you CAN use whole oats, or regular oat bran, the % of beta glucan is likely going to be lower, meaning you have to feed more, which means you’re bringing more starch to the table.