Yes, I agree, the cruiser benefits from a lot of "cross bracing" inside due to the aluminum interior so the box has no risk of going out of square without it being in a major catastrophic accident.
Here are a couple videos of the Cruiser "offroad". Having been offroad a number of times in the Cruiser we have all the articulation we need. Our camper is far too large to be a rock crawler so we don't attempt that as we travel alone most of the time. The cruiser was designed and built so that we would be comfortable on any surface and we haven't ever avoided a surface due to any limitation other than size. We want to be able to get off the road and park by that creek or at the bottom of that mountain that those people in a Winnebago cant get to. so far so good.
Could we have used a subframe, sure I guess. Do we need one, not so far.