My understanding is that aura does work the way it does in the show. It's very much like popular interpretations of chi and so on. As a thing of game balance, people with exceptional physical capabilities have a weaker aura, or less chi, than those who don't. So they can still do aura stuff, but they can't do as much. The more magic stuff plays off of semblances and weapons empowered by aura, so people who may not be as strong, fast and tough as other people have a greater abundance of aura, or know how to use it better.
But this doesn't exclude characters who have strong auras but aren't magicky types. My character, Willum, has a strong aura, but his semblance isn't very spellcasty. Instead, he's more of a technical fighter, and he uses his aura and fighting techniques to bridge the gap between him and say a more physically powerful character.