I don't understand why hopkins would want calzaghe at LHW?

IF he fights him surly he thinks he an beat calzaghe? there for what a story it would be for hopkins to beat him at sMW, stop calzaghe beating hopkins title def's of 20 and become a 3 weight champion? does he think at LHW calzaghe would be harder at SMW than LHW? i can't see his hand speed being much slower if slower at all, calzaghe has said numerous times about how hard it is to make 167, so a step up to 175 would if anything be better for calzaghe...?