Why release leads at a scheduled time?
Much of arbitrage is about developing a practical system and nurturing habits. Many people have full-time jobs on top of doing e-commerce, so it makes sense for there to be a predictable time to make selling a part of your schedule.
Why 9 am CST?
Think of it like the opening of a farmer's market: it's early enough to get first pick, but not so late that all that's left are root vegetables...