It's very nice of you to acknowledge that Williams did indeed develp without the playing time at PG, just as Sloan felt he should. Since then, Williams has acknowledged that, as much as he disliked how his minutes were handled, the experience was beneficial for him.
I don't know how well-informed go4jazz is on this. Maybe he can give us another comparison, on Fesenko's weight in June 2009 vs. June 2010 (they are probably not that different). Most players seem to gain wieght over the summer, even if only a few pounds. So, to say Fesenko only lost a few pounds is still to highlight the excellent job he did on his conditioning this summer, contrasted with what he did not do previous summers.
That said, even 9 pounds (assuming go4jaz's numbers are more accurate than the ones from Fesenko or the media, that what it would have been) means just over 3% bodyfat (again, assuming there is not added muscle mass, which with all the conditioning, you would expect). Reucing your bodyfat from 15% to 12%, or from 12% to 9%, makes a difference. You ever walked around all day with 5-pound weights strapped to your ankles?