There are a lot of stops that aren't on bus schedules. The ones that are on the schedule are generally time-checks for the driver, they can't leave until the time in the schedule.

For minor stops between scheduled stops, they only need to stop if someone is at the sign or pulls the rope. If you use one of these, it's a good idea to make sure you're at the stop by the time the bus can leave their previous major stop.

Delays are delays, busses get stuck in traffic too, and sometimes dispatch has them go off-route to get around accidents/ construction.

Source: I drove for PVTA during college.