Maybe i Just never noticed because in old engine it was so hard to keep a player from playing all season, but have you always not been able to rescind a redshirt after season had ended. I thought you could pull them on and off until the next season loads, but that does not look like the case.
I just took over a team which had a player that had not played and so thought I would throw out a redshirt to save me another year, but He did not like it and can not take it back. I thought you could always undo it if they complained, but like I said never did it after season ended, but I figured until it cycles over to next years stats that should not matter.