I started off thinking the Optionlock applied to the Protagonist in the OS, then just the OS itself, but a comment by Chris about the antagonist in Ghostbusters having options made me go through podcasts and realize actions of both should be realized in terms of the optionlock, not just reactions to each other. Thirteenth Floor has an MC seemingly with options of tracking down whodunnit, but he's not the protagonist. The optionlocks seem tied in with the driver turning points. I wondered if the driver characters (protagonist, antagonist, contagonist, guide) each tend to have optionlocks. The Passenger usually wouldn't, otherwise they wouldn't be passengers in the story.
Since the Story Limit brings the story to the climax, it seems easiest to tie the limit, optionlock or timelock, to the Story Goal in the Overall Story throughline. Once the limit has been reached...CRISIS, CLIMAX, CONCLUSION.