There is a following invocation in #processPartial method:
PartialVisitContext is instantiated directly here instead of leveraging VisitContextFactory.
This basically disallows use of VisitContextWrapper as a way of enriching tree traversal performed by PartialViewContext's.
In RichFaces we could replace ExtendedPartialViewContext concept by VisitContext wrapper with same functionality, leveraging Mojarra PVCImpl. This can lower the number component-library inter-operability issues and make partial view rendering less error-prone for developers.
Note: MyFaces leverages VisitContextFactory correctly: