As written, the Story Limit is a confusing optionlock. It is not a timelock because the Story Limit was not locked.
All this speculation is silly from a story creation context because you're looking at it backwards. A story has a Story Limit of a Timelock or an Optionlock because that is what the author has chosen. BOTH are possible choices until one is decided (from a story creation point of view).
From a story analysis perspective, you must look to what the author gives you -- which is why it can be wishy washy if the author is not clear.
The importance of the Story Limit is that it gives the story a boundary that tells the audience the conditions necessary to bring the story a climax, final confrontation, and ultimately a resolution. I like to think of it as the size of the story, which is why it is important that the audience understands what the limit is. Even if you aren't explicit, the audience will pick up on it if it is there. If it's not there they won't have a clue when the story will end (timelock), or what is necessary to bring it to an end (optionlock), and the story will feel like it meanders along without much direction.