Broken breadcrumbs?

On the demo and skeleton site, the default page is "Basics." If I go to the "Overview" subpage, the breadcrumbs say

`Basics > Overview`

That's what I expect. What I don't expect is what I see if I go to, say, the intermediate page:

`Basics > Intermediate`

I've searched far and wide for a setting that will fix this. Intermediate _isn't_ a subpage of Basics, so the breadcrumbs shouldn't look that way. All my efforts to find a setting in user/config/system.yaml and user/config/site.yaml have come up short. What's the fix to this? There must be one, because the Grav documentation site (https://learn.getgrav.org/) seems to work just fine.

Thanks for the help!

Reproduce the breadcrumb behavior on the demo and skeleton site, then inspect user/config/system.yaml and user/config/site.yaml for relevant settings. Compare the hierarchy with the Grav documentation site; done when Intermediate no longer appears under Basics while Overview retains the expected breadcrumb.

Written by the indexing model from the issue text.