I think you got it locked down Demon. Sheridan did make sure that it was only EarthForce ships that took on Earth in the final battle. Once Clark killed himself, that battle ended and he called in the coalition of worlds's ships to help try and take out the planetary defense network before it got to blast the planet itself. But the battle at Earth was only Earth ships. White Star ships were used at Mars and against the Shadow-Earth hybrid ships purposefully to hold as many of the EarthForce ships in ready for use against Earth directly. Similarly, I would say that the White Stars were used in the liberation of Proxima. Mars and Proxima being declared independent states, it wasn't a direct Earth v. Earth battle, but a free coalition of worlds v. Earth.
(Of course, my memory is subject to failure, but that's how I remember things going.)