OldGuy, I do see what you're saying. If a relationship is healthy, it's healthy. However, I would argue that most monogamous relationships, even healthy ones, are founded on a mutual, generally unspoken understanding that jealousy, insecurity, etc. are in fact there. In healthy relationships those things just don't get triggered, so it seems like they don't exist. But they are in fact still fundamentally there. Maybe this is a discussion for another thread, I've been considering starting one on jealousy and insecurity.
And by the way, the things you listed that indicate a lack of emotional maturity...personally, I would say those things indicate the opposite.