I would put it as "when it isn't too tricky to do so write your program such that data flows one way".
When data flows downwards it's often simple to have the top layer own and then pass down references.
But if you start running into lots of issues doing that it's probably a fundamental issue with your architecture. So you need to either rethink it or give up and try a different kind of approach. Both are valid, but I think people who try to muddle through without either dramatic option are the ones who end up very frustrated with Rust.
When data flows downwards it's often simple to have the top layer own and then pass down references.
But if you start running into lots of issues doing that it's probably a fundamental issue with your architecture. So you need to either rethink it or give up and try a different kind of approach. Both are valid, but I think people who try to muddle through without either dramatic option are the ones who end up very frustrated with Rust.