He's wrong. Every book has rules that the characters have to abide by. Without them, the book is pointless. So those characters have limitations, too.

And as for being a wizard, until he can produce a patronum, Jobs isn't more wizardly than Potter.

Did I miss something? It doesn't say why Jobs is a better wizard than Potter, does it?

It's summed up in the last point. What makes Jobs and Potter magical is their ability to be extraordinary and do things that normal people (or wizards can't) through their creativity ect, and to amaze us with what they can accomplish. However what makes Jobs better is that his magic is real.