it is different, as his mandate comes from having a majority of parliamentary seats, not votes. its also different as most parliamentary seats do have a majority turn out, and as i've said before i certainly would say they change the law so a minimum turnout is required.
He doesn't have a majority of seats though, he is the leader of the party with the largest number of seats but certainly does not have over half of the MPs. I would agree that there should be a change in law with regard to strike ballot mandates but equally I would, at the same time, like to see voting in general elections made mandatory!