In Les Miz the actress playing young Cosett and young Eponine don't bow. The only times they do bow is after an afternoon preformance. Only because they have to stay around till the evening one. But, I think that duringan 8 PM show after they do thier parts they go home.
Also, it's not unommon to have people who are understudies and standbys backstage singing as part of the chorus. There are a lot of shows that need more voices then are on stage and so they hve the understudies and standbys sing off stage.
"If you try to shag my husband while I am still alive, I will shove the art of motorcycle maintenance up your rancid little Cu**. That's a good dear"
Tom Stoppard's Rock N Roll