It is just a note. I don't mean it to sound anything other than what Wikipedia itself states. I see a tonne of "Wikipedia agrees" but none of "Wikipedia is a living document" and it isn't its place to be a gospel of truth...
Wikipedia is not and cannot, as per their own policies, be the primary source. 'Wikipedia agrees' is shorthand for 'the sources mentioned by this particular Wikipedia article agree'
I think it's shorthand for "the collective Wikipedia editors agree," which is not exactly the same thing as saying every claim is backed by any particular source.
You see none of "Wikipedia is a living document"? I think people are pretty aware.
You see a lot more cases of people quoting Wikipedia on a topic than talking about Wikipedia's trustworthiness because it adds a second dimension. It's [Wikipedia, Topic] vs. [Wikipedia].
I might look up 100 different things on Wikipedia. The fact that Wikipedia has all sorts of flaws is something I only needed to learn once.