Relative to “channel drift”, this is certainly a thing. My explanation for a lot of it is, as channels were being created, mostly back in the 90s, people said “hey, how about an all * channel?” Which sounded good until everyone realized that all of the A level * was still on the OTA networks and the mainline cable channels, and they were left with niche stuff and drifted into reruns.
I will always say that the killing of TNN was a huge mistake. That channel, while, yes, it skewed rural, old, and poor, had a real presence that it has not had sense.
WGNA to NN is a little more than “channel drift” IMHO. It is the abandonment of what, IMHO, is a dying format, the “general rerun” channel and trying to come up with something to avoid just shutting down and walking away from all those carriage slots on all those cable systems. This is not the last we will see as this genre slowly dies.