So I followed the steps, and then followed the steps again, and then again. Each time was without success. Vertex groups and bones were named the same, but the whole thing came apart. Parts were not even linking up with the bones, so they would not even move along with the rest of the broken mesh.
I unparented and re-grouped, applied scales, rotations, and modifiers, all without avail. I did this about three times to make sure that perhaps it was some step that I missed. I looked up the various answers, but the problem remains the same.
The only thing I know for sure is that when my model is in rest position or in edit mode, it all clips back together. Go back to object mode or post position, it all comes apart.