I'm the author here. I can tell you about my methodology for ordering. I immediately talk about text as soon as ownership and structs are explained. In Tour of Rust, I tried to hold to a principle of not explain concepts before their dependent concepts have been mentioned. I believe it's what allowed me to keep most of the pages as simple as possible.

I felt the procedural programming aspect was best explained with as little strings as possible, and wanted to get that out of the way as soon as possible.