Beet pulp is used for fill which has to do with their mid section and guts. Never heard of it causing brisket that is usually from fat deposits. We feed beet pulp to everything and it is a great way to hold animals because it makes them feel full.
IMO Beet pulp can add fat to the front lower 1/3 I have seen it happen, but don't know what causes it possibly the molasses in it. We try to use cottonseed hulls to add fill when were trying to hold one.