Oh great, that's the part where most bevy tutorials simply stop. They explain how to handle the ECS and then it's over, not even explaining how to render stuff.
Well, the ECS is how 90% of people will render stuff, to be fair. You don't need to worry about any of this stuff if you're just using regular sprites or models.
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.