One reason why a bike could be rugged is the presence of suspension elements to absorb the impacts from landing. This reduces the stress on the frame by a big amount. Another reason for ruggedness would be a very strong frame such as a BMX.
I don't think the Swift is rugged at all in that sense. I would not be comfortable doing jumps and wheelies and stunts on it or on any other folding bike, except perhaps the BF Llama but I don't know that bike at all. I would not even trust the Montague because the frame rotating joint under the top tube sees a lot of stress concentrated on it, and besides the tyre there is no suspension element to absorb some of the impact that would be imparted to that joint. I have seen a failure reported on that joint, although it is not clear to me if that was a copy or genuine, but to me even the genuine article is not designed for jumping.
DEBCAR's account of his use of the Dahon Jetstream to do proper trail MTB riding, details all the failures he has experienced and how he fixed those failures over the years. And that is a full suspension bike. So not even that was up to regular MTB-style punishment. And no doubt it wasn't designed for that either. The full suspension in that case is small travel, a big difference from large travel suspension as on a dually.