The seraph path-mapper is still requiring that users have confluence-admin group to access anything under the /admin URL.

Steps to reproduce:

Create a user, not in the confluence-admin group
Give that user ADMINISTRATE CONFLUENCE permission
Log in as that user and try to go to the admin console
You'll be prompted to log in.

Annoyingly enough, this doesn't seem to happen when running in the development environment (hence it not being found during testing here), but I've verified if on conf.at.com

A quick solution would be to remove the path components from seraph-paths.xml, since we've protected the admin-only actions through Confluence's own permissions mechanism, but Mike recommends writing a path mapper instead so the two systems can work together properly.