You're right, I had it in my head he was referring to the rear camber and toe arms. Going spherical with the traction/trailing arms will also improve on-track consistency, the main drawback is NVH transmission of road imperfections into the subframe dramatically increases. There's also a possibility of losing grip on rough and choppy surfaces [at the limit] as there's no rubber to take the edge off the impacts. For example, this is why the Camaro ZL1 1LE is uses spherical bearings everywhere *except* the front and rear torque links.
So, if you're chasing those final tenths on the track, spherical trailing/torque arms make sense after you've already taken care of the basics [coilovers, camber, brakes, tires], however IMO for a road car, or even a track car where you're predominantly on rough tracks, the negative outweighs the benefit.