Yes, I had tried that step also, as the original post described. It did not recalculate submission grades. When I did my own assessment of each workshop, THOSE grades were factored in, but the assessments that had already been saved did not change.
I did see (in another thread, I think?) the recommendation to use the "Clear assessments" tool from the Evaluation phase. However, I did not try that because I was not 100% confident it wouldn't erase how the forms were filled out, and I didn't want to ask the students to go back in and re-save. They were already frustrated and I just didn't want to add any more stress.
I ended up just using my own assessments to determine submission scores. The assessment scores seemed to calculate as expected, so I did factor them in to the students' final workshop scores.
I see that this has been an issue for a while. Do you think this activity will ever be "friendly" enough to actually use? I had planned to present it to our faculty tech team as a possible alternative to traditional discussion forums in online classes, but as it stands now, I don't think the advantages are worth the complex setup and potential problems that may be encountered.