This is how the namespace mechanism works.
The namespace mechanism is originally proposed in This Thread
Namespace mechanism is applied on pages with slashes (/) in title. / splits title into hierarchies, so called “namespaces”.
Example: https://twitter.com/TfTHacker/status/1600583338028404736
To avoid creating the empty namespace pages, you may remove the slashes in title (or preferred journal date format), then re-index the graph. Those namespace pages would disappear if there’s no content inside.
Related: preferred journal format