Hmmm crud. I tried to repro it from a blank slate: build brick, componentize brick, make wall, fill with component bricks, make house, fill with component walls. Add house component, then add wall to same scene. Bricks in the Wall do not show up as Brick_red#1, as expected.
I need to back track and see how the current versions are different than this repro step.
(Thanks for the replies!)