Inheritance of elements from site descriptor quite broken

After updating to 2.0-beta-6, I never get proper site output for multi module projects. I attached a simple dummy project that shall help to reproduce the problem.

When I perform a reactor build of the site (i.e. "project-parent> mvn site"), the pages of the sub module project-module-1 properly inherit most of the decorator elements, except for the custom "overview" menu. That is, the site of the sub module contains the menu configured for the parent project despite the sub module specifying its own menu.-

In contrast, when I only build the site of the sub module (i.e. "project-module-1> mvn site"), many decoration elements are not inherited from the parent's site.xml like <version>, <bannerRight>, <skin>, <links>. However, now the sub module's site properly outputs its own menu items (i.e. "Module-Item" instead of "Parent-Item" for the attached projects).

This issues might be a duplicate/relative of MSITE-256 but as I cannot safely judge from its description, I opened a new issue.