Are the frames the same but the lenses different between half jackets and the XLJ? Do either lens fit either frame?

yep. same frame for both lenses.

Generally any frame that has a larger or smaller variant usually only differs in the lens shape since it's easy for them to mold one frame and just cut different lenses. Same goes for Zero S/L, Dartboard L, and all the Why 8.x's

Also for the Halfwire