It could very well be that the owners of those two repeaters are unaware of each other. When you are in a mountainous area in Tennessee, the signals can go quite far and since you happen to hear them, I assume you are in a good location to hear both repeaters. That does not mean 90% of the actual users of each repeater are experiencing a problem 90% of the time. But if you hear a lot of regular traffic hitting both repeaters, than yes it may be a problem needing attention. The custodians of those two repeaters could coordinate a change of tones between them. That is a normal thing.
Looks like they may have discovered a legal method of linking!