It was also painfully obvious the rest of the cast were just using the available uniforms from DS9 (except for Stewart and Spiner, who had custom ones made for them). The extras in the background could be chosen to fit them, but not the principals; as a result, Riker's sleeves were way too short and had to be rolled up to disguise the fact, and LaForge's sleeves were way too long!
Didn't they have to squeeze Frakes' frame into Avery Brooks' uniform?
As far as the odd mixture of uniforms in "Generations," the sasme thing happened in TNG season three. That was sort of a transition season, with the main cast wearing new uniforms (which were slightly altered during the course of the first part of the season to eliminate the front seams) and most of the extras and background characters wearing the old first and second season uniforms.