Finders seem to be broken in some situations with polymorphic domain classes

With the Weceem plugin I have found that Grails 2rc1 gives incorrect results for:

WcmContentFile.findAllBySpace(space)

What happens is you get back all content nodes where x.space = space, not just WcmContentFile and descendent types.

The graph is like this:

WcmContent <---- WcmContentFile <---- WcmContentDirectory
           <---- WcmFolder
           <---- WcmHTMLContent etc.

The above query should return only WcmContentFile and WcmContentDirectory but it returns all types.

I tried to isolate this with different domain objects but could not. The only isolation I managed is to install weceem plugin into a fresh app and test a query at startup in BootStrap. This shows the failure in an app that uses weceem plugin.

The attached bug-report app includes some test domain classes that attempt to mimic and isolate the ORM hierarchy that causes the problem but to no avail yet.