Yeah I'm not sure there is much benefit to having super-stiff mounts on a longitudinal engine anyway. The shifter engagement is much more direct/precise than on a transverse-mounted FWD-style Evo, for example; and really all you ever gain from stiffer motor mounts is more precise shifter engagement (fewer missed shifts during WOT operation where the engine is torquing about).

For AWD and FWD vehicles, they can also help with wheel-hop to an extent; but again, not an issue for the Z.