If a horse tends to over reach and pull shoes then bell boots certainly can help, BUT not the snug, shaped fitted kind, In order to help protect the heel of the front shoe from the hind toe the have to be the old fashioned round rubber kind (with velcro or not works) and large enough to hang over the heel of the shoe.That means the back of the bell boot should just touch the ground when the foot is on the ground. A smaller one will not cover the actual heel of the shoe. With a big enough boot the hind toe will get stopped from grabbing the heel of the front shoe.
However most horses who get trimmed and shod PROPERLY do not pull shoes unless they stomp flies, or paw at wire fences or other objects. Most chronic shoe pulling is caused by farrier induced hoof imbalances.