The thing that you need to realize (my family lives in UAE) is that many people do travel a months time and during this particular time (2-3 months) the weather was all dusty. I mean you leave a car for couple of days and it gets ALOT ALOT of dust - especially if you live close to a construction area. (the probability of being around one is VERY high).
If this person had to travel for a month or 2 -- I wont be surprised it would look like that. But again - he should garage it or give it to someone to take care of it. On the plus side, the dusty windows will prevent the interior leather get direct contact with the HOT sunlight!!