The article mentions mutual interest could be a subtype of fun, but they wanted to make a distinction between when getting together is the goal and when there's

The article mentions mutual interest could be a subtype of fun, but they wanted to make a distinction between when getting together is the goal and when there's another objective beyond that. For example with drinking, they seem to think there's enough of a difference between the friends that get together to have a few drinks and the friends that get together to do a wine tasting focused on a region of France.