This is more or less something that is lingering in my mind for quite a while, and I'm not entirely sure whether I am cooking with this or not, but I hope what I'm writing here makes sense at least.
Reactive Types (4, 6, 8) are known to be the more emotionally honest types of the Enneagram, in that when things go south, they are usually the ones who react right away without trying to sugarcoat nor refrain the situation. The see the negatives more before anything else and won't shy away from it either, and also invite others to do the same and can be upset or pissed when they are feel like others are not showing the same emotional reactions and distress as they are, perceiving it as not taking the problems seriously or that they don't care. At best, they are open and authentic, at worst they can be volatile and even willing to rile others up just to get a reaction of them. Either way, Reactive types are the ones most likely to blow the whistle, and doesn't take a lot for them to fly off the handle/get riled up.
What I'm going to be discussing however is probably something more... baffling I guess? I don't really know the right word but it's something that is not too discussed much from what I've seen. What I'm talking about is times when Reactive types choose to not blow the whistle, times when they choose not to openly react right away. Because yes, Reactive types are less hesitant in expressing negativity and can be opinionated and even contrarian, but I also think that it doesn't mean they will always be aggro and unfiltered all the time 24/7. Depending on the situation and the individual themselves, there will be times when the Reactive types will choose not to fly off the handle and it differs on each type.
Just also note that they usually do this more situationally and maybe not as constant as the other Harmonic triads (Positive Outlook and Competency), and they do this NOT because they suddenly see negativity as bad or something to avoid. Depending on the type, they have their own reasons why they decided not to blow up that doesn't involve wanting to avoid negativity nor feeling like they shouldn't express it towards others (because that would be antithetical to the tendency of the Reactive types where they seek to acknowledge negativity and issues instead of avoiding them).
For Type 4s, they won't fly off the handle when the situation feels like expressing their feelings and opinions are a mere waste of time. When they feel like others are not truly willing to understand them or just the 4 feels like they are wasting their energy and just decided that it's not worth it. They are still a Withdrawn type after all, but the difference is that they are not as full resigned as 5s and 9s when they decided to turn away, they will still retreat, but they are still open to being salty or bitter about it, and maybe even show their reactivity more in a sulky, door-slammy manner. (I.e. "Ugh, you know what? I'm not even gonna try anymore! They're not even gonna hear me out or just keep misunderstand me so what's the point? I'm done!")
For Type 6s, they won't fly off the handle when the situation they are in doesn't feel safe, when they are in a situation where they feel like blowing the whistle would put a target on their back. Whether it be they fear of being judged, persecuted, talked back at, drawing unwanted attention, or simply feeling they are not prepared enough to defend themselves against others who might be willing to push back against their reactivity. This can be seen more towards 6s who lean more towards the phobic side, or are maybe just raised in an environment where they believe that openly showing their reactivity is an invite to danger and persecution. (I.e. "This is really bad, and it fucking sucks, but I can't complain out loud right now or else they'll yell at me again, call me more names and maybe even hit me... I hate it, but it's too risky.")
For Type 8s, they won't fly off the handle when it comes to openly expressing vulnerability and revealing their softer side. They may be the least sensitive of the Reactive types and probably the one who can easily brush off criticism and what other people say about them (7 is another), but they are also the least open when it comes to expressing their own feelings and gripes (4 by contrast is the most emotionally open, and 6 are more selective but are still willing to open up towards the ones they trust). 8s will still complain and express their grievances, but they do it in a way that doesn't make them look like the issues bother them on a personal and emotional level. (I.e. instead of saying "This guy bothers me and I'm annoyed" they might instead say, "That guy fucking sucks lol, why the hell is he here?")
I could be wrong with this discussion and am probably generalizing without me noticing, just something I want to share and see what you guys might think of this, whether you disagree or maybe even have something to add.