But, if the ball is coming off slower off the barrel, that's going to rob Rose, or any player, of a couple of infield groundball hits. Balls that should be getting through the infield at regular speed were probably dying because of the hollow bat.
I don't doubt that a lighter bat would help Rose... Hell, that's why they have the 3 ounce rule in HS/Little League. A long bat that is light is a very dangerous weapon... I just imagine cork could have a negative result on any hitter... specifically, if as Myth Busters said, the ball comes off the bat "markedly" slower than a regular bat.