Not much experience with the OWE (did a couple soon after they came out, none for a long time) but I would speculate that reroutes caused by weather delays constitute involuntary rather than a voluntary changes, and therefore segment limits are not applicable. Of course the downside of an involuntary change is that you tend to have to take what's offered, even if it is less than ideal. You might find some interesting info here and here which I found after a brief search.