While utterly a theory and may be easily disproved by someone more knowledgeable in the workings of lightsabers, I'm thinking that heat coming off the blades when combined with the super fast rotation speed could lead towards a rising vortex of air or the like?
They can't function as regular blades, that's obvious, since they don't actually have any physical mass to push the air down. But they do generate a nasty amount of heat and heat tends to rise, so spinning heat leads on to vortexes and rising air plumes and the like so..leading to lift perhaps?
Whether it would be enough to lift the bodies of the wielders I'm unsure of, but seeing how customized the Inquisitor blades are it wouldn't be hard to imagine some micro propulsion unit or gravity equipment built in to help with the lift (no evidence visible to this), that and the force of course could be enough to lift and direct them through the air even if just in the form of a big jump with no real flight ability.
But theory! Just wanted to share some thoughts as I quite like the idea and how they unitized it in the combat.