My exposure has been with the Mavic UST mountain systems not the road version but the principle stays the same. The removal of the tube reduces the flex/friction from the inside where the tube contacts the tire(debatable if talc makes a diff on it), as well as the reduction of tread mass can make traction/conformity better for odd surfaces. Results are vastly increased traction and increased efficiency.
In the case of the mountain system(Panaracer Trailblaster UST 26x195) I experimented on a mixed hills/flat perfect asphalt 20 mile commute route. Tubes with the same tires vs UST, no tubes with sealant added, the difference was 11 minutes deducted in favor of the tubeless. The other benefit, which is not always thought of is that with a tubeless casing you can add a much wider range of sealants than would normally go into a bike tube valve simply by unbeading one side.