That may be true in your local but sleeper work in my district is different from building to building. Pay is the same but how runs are bid and who covers them is different.
There are sleeper coverage and sleeper intent lists that can open the bottom seniority drivers to being forced on runs. We haven't had it happen yet but the company is saying the bottom person would be forced and I've heard the union agrees with this position because the drivers voluntarily signed for this work and have the option to get off the lists yearly.