i asked the same question to my shop and this is how they explained it because thats how it was explained to them at the ebonite seminar for the ball
the coverstock on the one is like a 12 ounce glass, while other coverstocks are an 8 ounce glass
i u pour 8 ounces of water into the 8 ounce glass it will be full so it will have no more capacity (losing rxn faster)
while with the ebonite cover it will stll have room to absorb oil thus lasting longer