Hello James,
The interaction behaviors are a bit limited in ProClarity Web Components for the Decomp Trees and Performance Maps, so it's not really about having it as a report from within PPS, you'd get the same behavior even if you are publishing in ProClarity Dashboards. The same limitations exist for version 6.3 as well.
There's a trick to get your Performance Map to drill down, and that is to include a grid in the same view (from within ProClarity). You could drill down on the grid and the same actions will be performed in the Map.
As for the Decomp Trees, it allows you to expand the nodes, but you have to click on the '+' sign itself.
Best Regards,
Karara