Maven 2 <resources> inheritance (parent -> child project)

Indeed, that's what the documentations says. But I confirm that Maven inheritance overrides resources instead of adding to them. This is actually captured in MNG-2751, and indirectly in MNG-2027, that you might want to bump.

TBH, I'm very curious to see what the maven folks will say on this (I'm personally happy with the current behavior, I don't really want child poms to be "polluted" by specific needs, like exclusions, in a hierarchy) and changing this behavior might break a lot of projects.

As noted in adding additional resources to a maven pom, this can be worked around using the build-helper plugin.