This recipe was designed to be a quick turn around. With extract you are only really sanitizing the extract with the boil as the maltster has done a mash and conversion. Also with this recipe the hop amounts are upped a lot. If you were to do a longer boil you would want to adjust the hop amounts to compensate for that or you will end up with an extremely bitter beer.
in general, if I come up with an extract recepe and shave some time on the boil, like say a 50 min boil or 45, you think it would come out okay, just be a bit week on the hops? So I throw in an extra oz. at the start and all is well?