Not all humans are equal, Aeon. Some are stronger, faster, more agile, while others are smarter and quick thinkers. He still has some magic in his human form, but it is a fraction of what he has when Shifted. He isn't helpless at all, so while he can't move several ton of stone, he can still manipulate a sizeable portion. 

He does have the increasing magical levels, I never said that they were without magic as humans. If they were, Lily wouldn't have been able fulfil her job as a spy. Take Liz, for example. She's pretty much exactly what I had in mind: She does have magic in her human form, but it becomes much more powerful when she Shifts. At any rate, Magic, like so many other things, becomes stronger as you train it/practice. If you want, you can have Gregory being a bit more powerful magically because of lots of practice. Same goes for Bright_Ops if you want Thule to have a bit more (eventually a bit better senses like I edited in at the end) than just a weakened version of the Howl. The part about his physical qualities as a human being only those he has trained himself to is set in stone, however.

Edit:
It's not because it's a new rule, as I have always thought of it like this, evident by Liz's ability to use magic in Human form (and still magic that makes her far more powerful than any mere human). I just forgot to mention it in the Intro Post.