Correct me if I'm wrong, but as a startup your metrics, learnings, and progress grows every single day, which means that applying early puts you at a disadvantage from your future self, let alone from competing companies, to get into one of those 400 interview spots. YC doesn't have the time and resources to re-review 7000 applications over and over again. If you re-submit later in this application cycle, you may not get reviewed again (I've regretted submitting early in the past, after our updated video with co-founders, vs solo founder, didn't get viewed at all.) Thus even with months of application time, it still makes sense for applicants to wait until the last moment to submit. Again, comment if you know more.
Is rolling admissions an idea worth trying out for YC - all teams start at the same time, but interviewing and admission decisions don't have to?