My insight about DADT policies, after reading the threads here, is that people tend to have very different understandings about what it actually is. I thought originally that DADT means that the partner does not know anything about the other partner's OSO, not even that they exist (definition #1). I have now learned that some people consider not sharing intimate details about their lives with one partner to OSO's being DADT (definition #2).
IMO there is a huge difference between these two. I would say that type #1 is almost impossible to be healthy, whereas type #2 can easily work. Some people just are not that keen on details about other persons' lives.