Just based on people I know, I don't think SJs are as common as many think. I consider myself fairly average and I know huge amounts of NPs and SPs. I probably know less NTs - to me, they seem more like a statistical anomaly.
The most significant thing about SJs that seems too stereotyped for me is the idea of rigidity. Yes, I do think they have a certain strong rigidity, but so do NJs; that's the nature of J itself. But because NJ is more conceptual, they tend to create conceptual barriers, and you can see that in the "one-track" thinking that many NJs exhibit (no offense NJs, that's how you achieve your visions so well). Whereas SJ is more concrete, so SJs tend to create more concrete barriers, ones that we can see in the real world. So SJ is given the "rigid" stereotype, but the truth is that they are just as open to information as anyone else, and you can see this when you present solid concrete evidence to an SJ and they say, hey, that's a much better idea!, and let you take over. In some ways SJs are more open than NJs, because you can present an SJ with tangible evidence, whereas it's much harder to present an NJ with conceptual information, especially given that their own vision is more mired in the subconscious to begin with.
So to bounce off of that, there's this conception that SJ automatically means rule-following, but what I see that manifest more as is a willingness to defer to people who possess a greater quantity and/or quality of concrete information. The SJs I know are likely to defer to doctors/police/experts/etc, as far as I understand, because they believe these people to be more knowledgeable about their area of expertise than they themselves are, and therefore there is a general assumption that the people making the rules are more knowledgeable about the situation the rules apply to and why they are necessary or at least advisable. As a habitual rule-breaking NP, I can say that there have been quite a few times when I have been caught feeling rather stupid for breaking a rule I felt confining (eg, wearing non-slip shoes to work, since they are usually ugly and uncomfortable) and subsequently discovering firsthand why I probably should have just sucked it up and adhered (eg, slipping 3 feet across the floor and falling hard on my ass in an olive oil spill). Anyway, what that also entails is that when an SJ breaks the rules, they know good and well what exactly the rule is and why exactly they are breaking it and what the potential consequences are and why they are risking that.
Furthermore, I think the SJ emphasis on the past and on the cultural milieu is another aspect of that concrete-evidence usage. The past is a good touchstone because it's a wealth of information just sitting there, ripe to be used. We already can see in the past what worked and what didn't and why. It's not a guessing game, so why would we spend more time analyzing patterns that may or may not lead us to a beneficial conclusion? (My favorite NJ example, Hitler - that man sure knew how to get results, but, in retrospect, what a fucking awful mess he made.) The cultural milieu is also a good touchstone because it presents us with paths that we can see will currently work. Maybe they're not better than what could theoretically be done, but they're more likely to work. Hence NJs are very hit-and-miss, whereas SJs are more consistent. They're less likely to totally blow things out of the water but they're more likely to get steady positive results. And whether or not that's better really depends on your line of work - given a surgical procedure, I'll err to the consistency of the SJ every time (not saying an SJ surgeon is better, STPs might actually have the upper hand there, or more likely simply whoever has the steadier hand, but can you see what I mean?).
I'm not saying this can't manifest in an unhealthy way of being too willing to conform and assuming that others have more or better-quality knowledge when they actually don't, or being stubbornly attached to old ways of doing things, but I think the SJ stereotype is, as stereotypes typically are, overblown and misunderstood.
Obviously if SJs disagree with any of this analysis then please correct me.