Afterthought: I took another look at the boat i question and it appears to me there is an awful lot of clutter on both decks that would disturb the smooth flow of water. It would be preferable if any water taken onboard could leave as soon as possible without slowing down which seems unlikely from the picture.

So is this a poorly designed boat, was it intended strictly for flatwater, or has the boat been modified from its original plan?

A boat with all that stuff should handle some cargo under hatches and on deck for which there should be added buoyancy. The paddler is light (by my standards) so it hardly seems the boat is overloaded. It's a lovely looking boat, but either there's something wrong or the boat is being used inappropriately.