I've yet to see anyone provide any evidence that the trims were added later. We've asked numerous people at SFGAm at TPR events, Media Days, and construction tours about them, and they all say to a T that they've always been there, and that the trims are actuated by the trains weight, and always have been. The heavier the train is, the more the trims activate. The lighter, the less likely they'll turn on.
We've discussed them ad nauseum in this thread soooo many times.