It's a bit unclear in the rules and especially hard to judge when the final level ends with a skippable cutscene. Sometimes I accidentally skip it myself.

The run ends with you touching the goal of mountain chase, the screen fading to black, and then 3 frames later the cutscene starts (the first frame of it appears). So if you're like me and trigger happy with cutscene skips, you can re-time by looking for the first pitch-black screen, then advance 3 frames in your video.