There are at least two things that this can mean.
First, it can mean that a given cultural group can be either privileged or not. A cultural group might be at the top of the social hierarchy and be respected. On the other hand, it might be at the bottom of the hierarchy and looked down upon.
Second, it will mean that cultural groups can keep those things that make them unique. If there is strong social stratification in a society, groups will not mix with one another. The cultural values and norms of a given cultural group will not be diluted through contact and mixing with other groups. This will lead to more cultural diversity in the society.