Well, I don't know if I'm the one who is misunderstanding this, but I think one should do a little talk about this exact topic.
Thi might expecially be important with this wiki: howto:post_relationships. And in the last few days, I was changing back parent and child post relationships and they ended up being reverted or I reverted a relationship xhange of another user. That said: It seems that there should be some clarification how to use the post relationships and when to parent a post.
Because right now, this list suggested there is nice and dandy, but appsrantly it needs some clean-up. So maybe there are some idea how to improve this.