Sweet Potatoes, Rice and Oats are almost the always go to carb sources during a prep. So, why not Beans? I would ask my coach but, I don't wanna bother him with every weird question google didn't answer.
This is not a way of going around him or trying to get permission from some where else. I will not eat them because he says not too which is enough for me on a objective level just, not so much on a for future reference manner.