Often times, I find claims of "whataboutism" to be unfounded. In this case, the editor chose to present a specific quantity in the article's header. Now, this quantity may be accurate (I don't know why someone would lie about this), but I would assume that most readers would not know how to put it into context. And I would also assume that the editor likely was aware that most readers would not know how to put this into context and that they would think that the number was really big. And your comment provided a useful reference point - a lot of things probably use gallons of water, and maybe the obvious narrative you would get from the article would not be entirely accurate.