What's your take on sp/so? I feel like there's a lot of misconception about that stack. People say one of the biggest sp dom traits is being reserved and private but would that happen as well with a contraphobic ennea and an extroverted mbti?
I dont have a "take" on Sp/so. My opinion on it is that it is overrated for stupid reasons, and that it is not best or worst than any other. But you're right, there are still a lot of misconceptions around it, and more so because there are still disagreements and a blurry territory when it comes to IVs.
Personally, the main misconception i noticed surrounding this stack is as follow:
The idea that Sp = Withdrawn, and so thinking Sp/so are automatically introverted whatever their type.
This is the worst lie ever. If someone is withdrawn, look at their core and fix. Withdrawness is caused by enneatypes, not IVs. I mean, there is a whole ass triad named as withdrawn, guess why! Sp makes people selective over what they share. Their goal is to preserve, but "what" they want to preserve is dependent of their core and fixes. Soc makes them decide what they share in order to gain more ways to preserve X core goal. So, yes, it makes them reserved, but reserved and withdrawn are two different behaviors.
Reservedness does not make one less sociable, or actually introverted, but as said above, more picky with who and what they share in their discussions. Withdrawness on the other hand consists of an actual act of retreating from whatever situation or people they are involved with, which is connected to typical introversion. Therefore, Sp dominance means in Sp/so that it makes them rather agile and selective in how they converse, but not necessarily introverted in the classical sense of this word.
To come back on your question, yes this reservedness will affect the display of reactivity and "expected" extroversion. Sp controls the flow of energy shared and given, in dominant position it means the priority is therefore to control what is given and taken. So, in an extroverted reactive type (4,6,8), Sp/so will make their reactions much more controlled, however it doesn't make them less demonstrative of their emotional reaction. They will let you know very promptly as any reactive type (especially with dom extroverted function) that what you did reactivated them. It will simply be a Controlled Display, but still a Display of Right Now I am X Emotions and it Displeases Me. Reactivity doesnt mean explosion, it means displaying the emotions the moment it is felt. But an Sp/so reactive type could very well explode if Sp determined that to restore and preserve whatever they aim for they need to show you your place (x soc). It is simply much more reserved about it, since they know exploding is energy taxing. Think Sp as kinda calculating.
Cp enneatype Sp/so simply counter act in a much more steady way, but overall it doesnt do much of a difference. They are still cp and so proactive against their fear. People tend to confound cp types with reactive components (wing, fixes), this is why i spoke of 4,6,8 specifically. But in the end, it is not the same deal, and cp is not a demonstration of affect like reactive type are described to be.
So, it is true it will make an Exxx 4/6/8 type more tempered on the outward, but it won't make them less demonstrative or reactive, it depends of the circumstances and how to attain one's goal. The way they will be reactive will simply be different but nonetheless a quick reaction to let you know they got triggered. And their dom extroverted function will still be as outward as any extroverted function, but might not be as messy as a soc or sx dominance would do as those two exploit differently the energy within (ex. emotions) and around them. They will therefore not be less extroverted or suddenly become introverted, they will simply be less Loud and messy, which shouldn't be a qualitative to determine extroversion, cp or reactivity to begin with.
I'd reinforce that the level of introversion and withdrawness is more dependent of the cognitive type and enneagram core and fixes, rather than IVs. Even tho IVs affect how those energies manifest and are displayed, the actual level of energies depends on those aforementioned aspects. At this point, it is all about nuance and it can get hard to figure out when all those little details aren't well defined.
The other point i could highlight is how sx blindness overall is misinterpreted even in Sp/so, but id rather address the issue in another post. Just know that Sp/so are not soulless people devoided of aspirations and ambitions, those are fundamental human needs, so we all got that. They just do it their way, as any stacking.
I hope it could help, if you want more info or explanation, don't hesitate to ask and precise what else you want uwu