RoyB,
The Aussies build some nice trailers for off-road, that's for sure! I wish someone here would build some like that, but I'm sure they're too expensive for a major market here.
My guess for the OPs trailer is that it is a torsion bar type of axle, instead of a straight axle on leaf springs. I was mostly just being a smart-a$$ with my comment about a non-axle trailer. I figured it's either and independent set-up like the Aussie one you showed or torsion bars. Most likely the torsion bar setup if it doesn't have leaves.