Correct. Each target's documentation can only link to its direct dependencies' documentation. This is described in the original pitch post and there's also a section that talks about what some of the tradeoffs would be of allowing bidirectional links and how that creates an inconsistent experience if one of the targets can be imported individually.
Note that you wouldn't be able to configure the "Inner" target to depend on the "Outer" target because the code doesn't allow for cyclic dependencies (not documentation specific).