I would think it's a management call, not an angler-friendly call. The have to try to balance out the rules so that good numbers of both young and old bass are prevalent in the river. That's what slot limits are good in some cases. Protect a 17 inch bass and he'll eat a lot of blue gills, juvenile rock bass and even their own young.
Has to be a balance- but nature takes care of most of it too. I would think the upper end, being more shallow, less deep holes, wouldn't be as conducive to large bass than the lower, deeper part.
Or am I all wet? (I've been wet a lot lately)