You are correct the ailerons control roll about the 'longtitudinal axis' and what that statement would indicate to me is that in addition to the mounting provision at the wing joint for a single servo to control the ailerons through pushrods and torque rods on the ailerons, that they have also provide mounting plates out on the wing bottom somewhere to instead of using a single servo but use one on each wing operating the ailerons through short pushrods directly to control horns on the surface.

On a trainer in the training evironment they provide virtually nothing. For aerobatics they tend to remove some of the associated spongeness of aileron torque rods and will provide a little better roll control.

John