And then people use and rely on information like this to further ignite their cognitive biases. Seems more like promoting misinformation than anything.
The difference between that and the traffic modification API is the threat model. The third party were to compromise uBlock Origin's servers, they would have a frightening amount of power over millions of machines because uBlock Origin essentially self-modifies; it downloads new rules for what should be blocked. So that breaks the security guarantees Chrome wants to provide; they can't say that the lock icon on a website means anything if a Chrome extension is allowed to arbitrarily modify traffic back and forth as a man in the middle on the last mile and Chrome web store maintainers haven't looked at the source code it's running.
I don't think there's a similar security threat for cosmetic changes.
The only piece of reliable information is this: I once asked Google engineer whether they plan to support declarative cosmetic rules (that's what we do ourselves in MV3 and that's why the extension still requires wide permissions) and the answer was that they definitely do plan to do that in the future.