To add one more data point, we had this issue when installing content
packages from one environment A to another environment B. We expected
style classes installed via the package in environment B to carry
through to the publish instance on environment B, but that wasn't the
case. We were able to see the styles render correctly in both author
editor mode and "view as published" in environment B, but not in the
actual published environment post-publishing, because the classes
weren't being added ...