I'm not sure if it makes it unbalanced, except some people cant do it and some can, but then some cant take corners without clipping the wall, some can. Its a skill albeit a different one to the normal racing skill set. It is less of a divider in Pulse though as the boost received from a barrel roll has been reduced (as indeed has the boost from a trubo start), plus the energy drained from performing one is now a % not absolute figure meaning each ship can in theory perform the same amount.