First off it would make it a whole lot easier rather than skipping cutscenes multiple times. Second you can tell if it's a real run by looking at the mission finished whether it has your best time, grade and score. You are unable to get "your bests" on custom missions even if you keep doing the same one. Unless there is another reason for us to show or if I'm wrong then I see no reason not to switch to make it easier for retries.

I will be editing the Individual level rules to now accept runs with only the in game timer.