I think that they will wait for the document, specially if you sent it on Friday and they still didn't respond (as this means that on Monday if they continue document will be there). I don't see why they would continue to decision and disregard the document if it was sent prior to decision and upon their request.
Out of curiosity, which visa did you have before, on what date and time did you pay for priority and were you able to immediately get biometrics?
I am going through the same process now, but still waiting for super priority - it didn't show up for days
Thanks!