Even if assuming considerable knowledge, it's nice to be able to refresh the reader on basics here and there. That text is largely just reserving the right to not explain everything (also I'm moving away from it in general).

Also: what example? There's like a hundred examples.

Edit: If you mean the examples here: https://doc.rust-lang.org/nightly/adv-book/ownership.html

They're a recurring example that we deconstruct in later sections. There's no need to make them needlessly complicated.