It could of had heavy duty suspension fitted. Anti-Roll bars cannot 'harden' the ride. What they do is limit the body roll when inertia is trying to roll the vehicle, although axle articulation is limited somewhat by the anti-roll bars but they do not hinder it enough to cause problems on greenlanes.
Out of personal preference I would much rather have one with anti-roll bars (and maybe even better, polybushes all round with Monroe Gas Dampers! :D )