I think hooking mortailiy on wild steelhead is more like less than 1% among CnR anglers.
here is why.. hooking mortality studies done in BC indicate that the largst amount of mortality came from loss of blood due to deep hooking. NOT due to the stress of being hooked. In fact studies have shown that the vast majority of hooked and released steelhead survive with NO ill effects.
Wearing a steelhead out to exhaustion or stressing them beyond what their bodies can tollerate simply is a red hearing and seldom or never happens. Hooked and released fish die when they have massive blood loss.. such blood loss comes from barbed hooks, multiple pointed hooks and bait that is swallowed. CnR fishermen rarely use trebels barbs or bait..
therefore CnR'd fish rarely have sever blood loss due to hooking injury and therefore survive at an extremely high rate.

Now would you like to explain why you think it's more on the order of 10%???