No doubt a single X meets the legal requirements but a series of Xs for the first few hundred metres wouldn't exactly cost a great deal and make the situation more obvious.
And I notice on that photo that the single X is offset from actual centre line. It's 15+ years since I flew professionally so maybe I should shut up. But it does strike me as odd that the symbol isn't on the centre (or extended centre) line precisely where a pilot looks when landing.