I think that very few people in general, in any area or from any socio-economic class, give twins themey names or names that are too similar. I think that the vast majority realize that it is silly, that if they do so they and their twins will encounter a large amount of eye-rolling throughout their lives, and they know that twins need a sense of their separate identities, which themey and similar names would be an obstacle to.
In my example, only
Mary Kate and
Mary Beth, and Lamar and
Lamont, were themey and too similar. I always rolled my eyes at
Mary Kate and
Mary Beth. Lamar and
Lamont are not quite as bad. But in my experience, those kind of twin names are in a small minority.