This fits my observations. It seems to be easier for some very small, tight-knit communities. I can see why migration would be more feasible for those.
The larger trend will probably be much slower. Lemmy and other solutions need to grow, develop, and do some search optimization. I suspect that the number of mods on Reddit will slowly go down over the next year or two. Hopefully, most will find a new landing place.
I followed the link as you suggested. I found a slight correction on the way it works.
A “shadow account” was some layperson’s attempt to describe what happened. That seemed clear to me immediately. It also seems that Threads and Instagram are much more intertwined than users expect.
I understand why this would upset people! I was furious when I tapped one screen wrong and connected my Facebook and Instagram accounts. It can’t be undone. It changed a profile picture. I didn’t quite become angry enough to delete both, but I stopped using them.