Does it not look right to you ?
No, it doesn't. That freckled browning on the plain pie is indicative of defective cheese. On the mushroom pie, you sauteed the mushrooms in fat beforehand, correct? If you look at the area around the mushrooms, you'll see oilier spots that have no browning. A good cheese will look like that on a plain pie.
I'm not pointing fingers- I don't think it's anything you're doing. But something's not right with the Saputo.
How old is the Saputo you're using? Does it grate pretty cleanly or is it a bit gooey?
I've never used this technique for pizza, but I've used it for long baked lasagna and it works very nicely- if you feel like you're happy with a darker rim (which looks great), then I might mist the cheese area with a little water right before baking. Just be careful not to get the rim or the peel. The water should both slow down the bake on the cheese a bit, as well as promote oiling off.