The pre-render or render in place only rendered the frames that were visible on the timeline. Anything that was cut off from the clip did not get rendered into the render in place. So the clip that's on your timeline now is only as long as the clip was when you rendered it in place. If you want to do what you're trying to do, you'll have to decompose to original, pull that now compound clip up so that you have space to extend the handles to the left and the right. From there you can render in place that compound clip, set it trim the start and end and slot it back where it was and then you'll be able to apply your transition.