It sounds as if Dan has just described the same issue I am having and was hoping for some clarification on. I just finished class. I had set the submission deadline for 12:00, the beginning of classtime (I had announced several times that everybody needed to submit SOMETHING by the deadline, or they would not be assigned a draft to review). Of course, one student had not submitted. It was ok because we're doing peer review for the first time and it's early in the semester--so I'm still training them how to follow my directions. However, another student asked after class if he could resubmit his draft--he had made some changes during class and wanted an updated copy available before people started to review them. I had moved it to Assessment, and he could not. I then moved it back to Submission, and he still could not.
After reading others' comments, I think the problem was that--even though I had moved it back to Submission, I had NOT extended or cancelled the deadline. So even though it was in Submission, it wasn't available (and, yes, I had enabled late submission).
So I guess the answer--if you want students to be able to have some greater flexibility--is not to use Workshop to enforce the deadline: leave it open but announce your own deadline and then enforce it as you wish. Even without activating a submission deadline, Workshop still timestamps everything, so you can see if something is late or not.
Of course, the above method does require you to move the Workshop into the Assessment phase manually, which is not ideal if you like the automatic switching feature.
To clarify what others have said, I believe th