I'm afraid you have grossly misunderstood the relationship between Ground Balancing and sensitivity. Of course your machine will false if you run it at sensitivity of 10. And it WILL hunt quietly at 4 with no falsing. If you ARE able to run the sensitivity at a higher setting, say 6 for example, that's fine. But the conditions need to be right. If you're talking about a CZ-70, there is little chance you will be able to run it above sens 4 without falsing, except in the cleanest of ground. And you will get about 95% of you max possible depth at that setting anyway.
Now as for the Ground Balancing...you are supposed to set the volume at 10 and the sensitivity at 10 when you do the ground balance procedure. You aren't supposed to LEAVE it there when you hunt. You're supposed to set the sensitivity back down to what works for your area you are hunting at the time and the volume to where you want it. Going up to 10 is ONLY for while you are actually doing the ground balancing. That seems to be the part you didn't get.
Let me tell you the way that most experienced CZ users do it. We use "The Bobbing Method". The procedure in the book is weak and not well written. If you want to do it right, do it like I describe below. I this wrote this in a post on this forum a year or so ago. Hope it helps.
<STRONG>The Bobbing Method of Ground Balancing:</STRONG>
<FONT COLOR="#ff0000"><STRONG>Note: Use headphones to do this