More reasons than just that. Overbuild drones while expanding (or even before) and then transfer to have a new base up and fully droned in construction time + 1

More reasons than just that. Overbuild drones while expanding (or even before) and then transfer to have a new base up and fully droned in construction time + 10s. You overbuild because you're going to lose 1-2 drones to any capable attack minimum. You can risk more on the defense when overbuilt. You have bigger chances of being able to expand during a base trade, ...