We still have a lot to learn of the psychology of the situation. Results from these studies are always interesting. Even if it is far from the real thing.
It is also a perfect starting point for a post apocalyptic novel. "The only group to survive the end was a small band of researchers, stuck in their isolation experiment."
I'm thinking a lot of the equipment is different as well, and since they mention simulating equipment malfunctions, that plays an important part, especially with the additional limitations/simulated dangers.
Antarctica trips have all of those limits you mentioned, they'll just be worse for Mars. While they can operate sort of freely for a few months, once winter sets in, they are just as isolated as another planet. They just get the advantage of easier setup then Mars.
Hard to say - There's still a lot of hazards yet to be accounted for: a lot more radiation exposure, literal poison in the soil, severe weather, safe and affordable supply chain, etc.
I think the radiation exposure might be manageable though, as at least in theory you can shield the habitats.
The showstopper could be the low gravity - we haven't really done many experiments on low gravity, the Mars Gravity Biosatellite never got built. But if it turns out that Martian gravity is really damaging to human health and thus long-term habitation is not viable then I think we'd have to really rethink our human spaceflight goals as on a planet you don't even have the option to simulate gravity via the centrifugal force - so it could just be game over for Mars colonisation.
I guess that depends on what you consider reasonable. I figure if they're starting with simulations such as this now, it's reasonable to expect an actual manned mission in maybe 20 years.