Yes, this is the classic trade-off between optimising the time it takes to get things done, and the time spent doing things.
If you want things to be done quicker, you counter-intuitively have to spend less time doing things. Keeping a person in reserve is one easy way of accomplishing that.
(Why is it a trade-off? Because when in order to ensure you spend a lot of time doing things, you need to have a long queue of things to be done so you never run out of things to do. That long queue means everything takes longer to get done because it spends more time queuing.)
If you want things to be done quicker, you counter-intuitively have to spend less time doing things. Keeping a person in reserve is one easy way of accomplishing that.
(Why is it a trade-off? Because when in order to ensure you spend a lot of time doing things, you need to have a long queue of things to be done so you never run out of things to do. That long queue means everything takes longer to get done because it spends more time queuing.)