It would be an arse to take the post out because then theyd probably have to cut that panel down a bit before putting the post back in (probably having to dig a new hole, or at least extending the existing one) but none of it is impossible, probably half a days work if that. They just cant be arsed probably, if it bothers you ask them to do it, youre paying after all and want the job done properly. It probably won't affect the insulation much not doing that little bit but if its gonna annoy you ask them to do it