Far too simplistic to say more time on the pitch = better player.
Perhaps the environment, the style of play, the balance with different team mates or many other things just suits him better at Porto and that's why he's getting more minutes?
He looked a tidy footballer in his limited appearances last season but it was never anything more than that. Think for the quoted price I would've wanted to see a bit more impetus. Few tidy give and goes, the odd sidestep away from pressure and that, it was nice to see but it was always in safe areas that didn't really achieve anything. If he'd been doing that closer to the opponents box fairly regularly, leading to situations like Moutinho's goal the other week, then I'd have been more convinced.