Why my Rust doc directory is common for all my Rust projects

I got criticized in one of my post why I put a documentation for the app inside its doc directory instead of putting Rust documentation there. So, I would like to get a wider opinion if I do something wrong.

Rust doc has a very neat feature allowing to merge documentation for projects or/and crates in one integrated HTML doc system. In this case, I do not need to switch from one documentation for some crate to another documentation for another crate, because all my crates already transparently integrated. It gives me a possibility to use a doc directory inside a project to document functionality of the application itself not related to Rust. Say more, users of my app even have no idea that Rust was used for programming the app. They can think that C or some other language as Go was used.

Do I do right, or you would suggest a different approach?