It seems to me like there would be a correlation between SO and Fe. That cold be completely wrong though.
I have thought this too and I have often scored quite high on so - like, I've had test results of sp/so or so/sp. But I commonly identify the most with sp/sx descriptions, particularly for type 6 specifically.
I do have strong Fe, but actually, the recent thread on the social instinct convinced me more so that I probably have so-last; or, if it's possible, maybe I am very close on sx and so. The thing is, I am very concerned with dynamics between myself and individuals - extremely concerned with interpersonal relationships particularly where I have something long-standing already built up with a person - a friend, a family member, a significant other. I am very preoccupied with the balance between maintaining personal space and autonomy, and reaching out to others (which I see both as a responsibility and as something that can refresh me). And I would like to play my part in keeping things running smoothly and pleasantly for everyone.
BUT, I'm not much interested in group dynamics. I often find them rather silly a lot of the time. I tend to think of them in terms of people who want to create unnecessary drama, and who are insecure. I find office politics laughable and don't understand why people get so hung up on them. I've felt uncomfortable when I end up in social settings where there are cliques and hierarchies. I mean, I have a feeling I'm being left out and possibly looked down upon for that, but I'm not annoyed so much by not fitting in that well, I'm annoyed that this sort of social structure exists and that societal pressures are making me worry about it at all. It all makes me think of high school and I want to tell the people who really participate in it to grow up.
You could say I'm interested in group dynamics in that, if I notice someone in the group who seems shy and uncertain, I am likely to make an extra effort to draw them out and be friendly. But trying to dominate the group myself; or trying to ingratiate myself with the top dog; or trying to establish where I come in the hierarchy; or knowing who the top dog is at all - I just find this a waste of time, and frankly juvenile.
I'm not sure - it's possible I am misinterpreting what so is about. But that thread touched on a lot of this and it made me think more so than before that I probably really am sp/sx. (I'm definitely not sx-first, either.)