The scheduled departure is 9 AM. If you are assigned a popular route, with multiple busses, you could depart as soon as 30 minutes past the moment disembarkation starts, but you won’t know until then. The busses are not direct as they cover multiple resorts, so you could be riding for an hour on WDW property before arriving at your resort.
If you get off promptly at the first available moment and grab a Uber, you could save 2h over the worst possible scenario with the
DCL bus.