I still don't understand how it makes a difference if the agent is a human or a bot?

There's no fundamental difference, but in practice the difference is one of frequency.

E.g. I sometimes have 10+ agents kicking off changes to the same small project at the same time, and likely to all want to merge within the next 15-30 minutes. At that rate, merge conflicts happens very frequently. The agents can mostly resolve them themselves, but it wastes tokens, and time.