The core problem with basically every single instance of boundaries discourse I see is that nobody seems to know what the word "boundary" actually means.
Boundaries are personal and social. They are based on mutual respect. Boundaries are not orders, they are requests, intended to establish a cause and effect: if you do this thing, I will do this other thing. "If you show me ship fic, I will block you" is a boundary. "You are not allowed to make ship fic at all" is not a boundary, that is a rule.
Rules are not boundaries. Rules are based on power and control - they are imposed upon you. This is not necessarily bad, but it must come with understanding of where they can be applied. Rules only apply where the rulemaker has control of what is allowed. And these are how many creators seem to approach what they call "boundaries". Again, this is not necessarily bad - their own twitch chats, discords, and maintags on social media ARE spaces in which they have control (some spaces more than others - maintags are shakier since creators don't have moderation power there, but that can be alleviated by creating a dni tag and asking people to place content there instead), and are therefore places where they can make rules about what they do or do not want to be shown. This is fine. Creators have the right to moderate their own spaces how they wish.
Where the problems emerge is that many creators seem to assume that they have the power to apply their rules (in the guise of "boundaries") in places that are not their own. Non-main tags on social media, archive of our own, private discords - these are locations in which the application (or lack thereof) of boundaries is no longer the choice of a creator. They do not have power; thus, any choices made by individuals in those spaces must necessarily be based only on the social agreement between fan and creator, an inherently parasocial construction. And in this case, the parasocial agreement that actually exists is not "this thing must never be created", it is "this thing should not be created or shared in my spaces".
I would argue that the primary issue in how "boundaries" are approached is a misunderstanding of how all of this works. Boundaries cannot be enforced in private spaces because there is no power relationship there. They can only be requested. As a result, when creators attempt to enforce boundaries in spaces that are not their own, what will actually happen is a series of barely-controlled harassment campaigns aimed towards people who are, by and large, following the social contract of boundaries but not the power-enforced contract of rules. And that harassment is far more of a problem than any person in a private discord writing something against boundaries. One might make someone uncomfortable.
The other gets people hurt. And that's where the line is crossed.
