Sorry :( I wasn't trying to defend it, I was just trying to explain to you where I believe it came from :(
In my experience, some hamsters like to climb, some to burrow. Tanks can often provide plenty more burrowing space than a lot of cages.
I'm not sure where you are getting the info that a smaller cage or tank is suitable for a smaller hamster such as a Robo? From what I have seen, Roborovskis are often more active than any of the other species so if anything would need a larger cage?
I believe you didn't read my post right... I ment that tanks (not twenty gallons, tanks in general) are more suitable for Roborovskis as they are a small species of hamster and tend to be escape artists (in my Experince anyway) and nearly always find a corner In a wired cage that they can squeeze through.
In my opinion, regardless of species be it a syrian or dwarf, all require a minimum of 500 sqaure inches. And if it's a robo, a minimum of 40 gallon (50 Preferbly) should be required. When I ment tanks are suitable for robos, I ment That robos nearly always escape through bars as they are the smallest species of domesticated hamster, therefore can be kept in large tanks of necessary to prevent them from escaping.