Trout looks a good prospect, but good prospects don't always equate to the real deal. Maybe the club just have not seen enough progress, not impressed on loan at Dewsbury, and maybe think we have better in Walters Alex Sutcliffe and others.
Or i suspect this may be a cash + long term loan for a year or two with Leeds have first dibs on him he he goes well in Super League at the Giants. Great deal for all parties, Leeds get to see if he cuts the mustard in super league, player gets to test himself, Giants get a great young prospect for a year or two and some hard cash for Leeming.