[DustyPorViva]

He is using a very simple image(and I must say, a very bad example for this kind of tutorial, give the random black outlines and such) for his tutorial. Rotating anything with a lot of detail and work would result is absolute loss of control and just mess it up.
In order to come out with a better outcome, you best just put the effort into actually drawing the other sprite... I mean, come on, you're only doing two images here. One straight, one diagonal. You end up just rotating them for the other directions anyways, it's not that much work.