Might wanna read it again, it's right there :)

The best architectures, requirements, and designs emerge from self-organizing teams.

It's an incredibly critical part companies love to completely ignore.

If you assign devs to teams and lock em down, you've violated a core principle

And it's a key role in being able to achieve these two:

Agile processes promote sustainable development.

And

The sponsors, developers, and users should be able to maintain a constant pace indefinitely.

This is talked about at length by the likes of Fowler, who talk about how locking devs down us a super fast way to kill sustainable development. It burns devs out fast as hell.

Note that it's careful not to say on the same project