You're right moo, I guess there's two different ways the dealer could be influencing it. If they're somehow stacking the shuffle so that high cards come first, then you'll see counts that always tail off negative.
If they're merely counting along, and shuffling as soon as the count turns positive (before that hand is played), then you'd see variable rounds between shuffles, with some short decks (one hand), and some longer ones.
Or it could just be dumb luck. But preferential shuffling is pretty easy to notice is you're keeping a count. I mean, even *I* noticed it when it happened to me.