I don't know for sure, but I will say that when steelhead or trout fishing, you will do much better if you can keep your stuff about 6 inches to a foot above them. Sure, I've had a few takes where the gear dredged into the rocks and a fish grabbed it, but my guess is they probably spotted/tracked it before it hit the bottom and when it dropped to the bottom, they angle down to snatch it.
That said, especially for beginners, it's usually more important to get low enough, rather than keep from getting too low.