I think you have posted a very good question. I'm no biologist but I do fish for Smallies and other warm water species in the rivers as much as possible. I believe it has more to do with the water temps below the Holston, Clinch and several other cold water discharge dams, than the fact that the trout have a negative impact. It goes back to the comfort zone of each species. The sunfishes prefer a warmer temperature range than the trout, so they would naturally move to warmer areas of the rivers. If the water temps constantly stay below this range , they won't spawn and inhabit those upper sections of the river. http://www.tnfish.org/SpawningTemper...essee_TWRA.htm
I have fished for Smallmouth on the Holston quite a bit over the past several years, and I agree that it is much more productive below Nances Ferry. I have caught them above it, but this past year with all the big releases from the dam, there seemed to be few smallies caught in those areas. I can remember water temps around 50-52 deg. at NF in August.
Maybe we should email Jim Negus or Rick Bevins at TWRA for some more info on this.