Behaviour of layer groups seems inconsistent in the capabilities document. Single layer groups will sometimes have their individual layers exposed as well as the group. When added to another group, single groups will sometimes be exposed multiple times, under the correct group and in the root.
Steps to replicate with Geoserver demo data:
View the getcapabilities document without making any changes to demo data.
tasmania only appears as a group in the capabilities document. tiger-ny and spearfish both show as groups as well as exposing their individual layers.
Create a container group and add the Tasmania group to it. tasmania group appears under the container group and also under the root.
Create a second container group and add the tiger-ny group to it. tiger-ny group appears only under the container group and not in the root, correct behaviour. However all of the components of tiger-ny still show up as individual layers under the root.
Go into one of the tiger-ny layers and uncheck the Advertised box so the layer doesnât show up on itâs own, the tiger-ny group then appears under the root as well as under the container group.