To close this loop, Support's response was that the user didn't use "add recipient" but shared the public link instead which is why those people weren't added to the workflow. I had my user show me how she shares, and she did it correctly using "add recipient." I have drilled into them, and they each have learned the hard way, that any other method of sharing causes problems that eat up hours out of their day (and mine). So there's no resolution, we can't repeat it, and I don't know what exactly happened.
They say that the loss of the SOCD on the notifications will be fixed next week.
As an added anecdote, I lost a good training method when Proof changed the language from Share/Share to Share/Add Recipient. We used to sing it to each other to remember that's what you have to do. "Share Share!!" It was like birds chirping. Jill Ackerman