I haven't been part of any major game development project, but from what I've heard, understanding the underlying operations of an engine is an absolute requirement for getting performance out of the game.

For simple example games it probably doesn't matter, but if bevy wants to become the de-facto standard for professional Rust game developers, it has to have documentation about the inner workings.

Event inside just the ECS, the scheduler is black magic to me. I've spent my free time last week trying to understand how Query works, but failed to get anywhere.