After I entered my last post, I did some research on the use of buttermilk to satisfy my own curiosity. I had heard of using buttermilk in pizza dough although it is rarely done by professional pizza operators because of cost and other considerations. The primary contributions of buttermilk are the butterfat content, which adds flavor to the finished crust, and the lactose sugars in the buttermilk that contribute to increased crust browning. Usually the crust will be fairly soft, in part because the finished crust browns up fairly quickly and the pizza can't bake long enough to give the crust a crispy characteristic.
When I researched buttermilk (liquid, cultured, lowfat), I learned that it constitutes about 90% water, 0.9% fat, 4.6% sugar, and 3.3% protein. A cup of buttermilk weighs about 245 grams, or about 8.64 ounces. So, in your case, if you are using 1 1/4 cups of buttermilk of the type referenced above, that comes to 10.8 ounces. If 90% of the buttermilk is water, then the water content is 9.72 ounces. You didn't indicate how you measured out your bread flour, but if measured out in the way recommended by the flour producers, 2 1/4 cups would weigh about 10.25 ounces. On that basis, the hydration based on only the water content of the buttermilk would be around 95% (9.72/10.25 = about 95%). It would be a few percent less if the protein in the buttermilk is added to the flour weight. Either way, the numbers would be unworkably high. I assume that you are using a fairly "heavy" cup in measuring out the flour or possibly you are adding more flour on the bench at some point. Can you clarify your methods in this regard?