I think the biggest advantage it would give them (which will be less apparent in testing) is it should greatly reduce tire wear over the course of a race. With toe angle fixed, it must always be configured with a good deal of toe-out to make the car turn in properly. However toe-out causes scrubbing on the tires on straightaways. Being able to adjust to what is best for the current direction of the car should allow the tires to last longer. Possibly significantly.