Nothing wrong with that, why you get to that weight you can see a huge fluctuation. Like even from meals and drinking i can see a 3-4 kg shift in my weight through out the day and im not that heavy. Its has always made the weight easy, id dare say he looks more ripped and in better shape than usual in that picture
Lol it's more the re hydration side of things, if i break a fast and eat for a day and drink you can see a 3-4kg weight fluctuation