That’s what I thought too, but I double checked and they do get packaged.
Anyway, modular control rigs are not yet production ready, so I assume that these packaging issues are within what Epic considers acceptable for now.
I know 5.5 introduced new features to modular control rigs, so maybe they fixed this while they were at implementing those. I don’t know because I haven’t had he chance to try out 5.5 yet.