I don't think it's the length of Will's trousers that was the real problem.
First of all, they seemed to start way above his waist. A tribute to Simon Cowell, perhaps? But it did nothing for Will's figure (which I suspect is not quite as svelte as it once was … not being weight-ist here, I might add - just an observation!).
And then there was the fit. They looked all lumpy round his bum, and the shortness of the leg only enhanced that.
I don't think Ore had the same issue with leg length, but they were really badly fitted, too, and possibly more noticeable because they were paler.
All in all, the kind of fashion shocker I don't expect from SCD's usually very impressive wardrobe department. Maybe they had work experience in? But why did the producers not step in and veto both those fashion disasters?