Answering myself here, it seems to be closer (maybe identical) to MDL-44330 Moreover, there certainly appears to be a constellation of related issues here:
MDL-44330 Assignment opens up the "wrong" student grading form
MDL-42306 Grading assignments - row number logic
MDL-52268 ATTO Editor not purge "not saved" draft
MDL-52004 Atto autosave restores draft for wrong student when grading assignments