Consider that demand for food delivery is not constant throughout the day and night.
I believe throughput would actually be reduced every time demand increases, which would happen in the morning, at various meal times, around the different opening and closing times of various restaurants, etc.
I do agree that the throughput reduction would be more complex than “1 driver sits idle for <delay time> every 1 order”.
Throughput would still remain unchanged. Suppose that the "lunch rush" is from 11AM to 1PM, and imagine that it's uniform for the sake of simplicity. Then drivers would end up being fully utilized from 11:10AM to 1:10PM, instead of 11 to 1. The 10 minute lag at the end where drivers are still finishing the queue makes up for the 10 minute delay at the start.
I believe throughput would actually be reduced every time demand increases, which would happen in the morning, at various meal times, around the different opening and closing times of various restaurants, etc.
I do agree that the throughput reduction would be more complex than “1 driver sits idle for <delay time> every 1 order”.