I don't disagree, and I'm personally aware of the consequences. Adding the API would be the first step, and future proposals and changes could amend it to add other environment details to tell a website that there are browser extensions that can read or modify the page.
I don't really think summarizing WEI as though it already includes those really helps people understand what WEI currently is or does, though. Nobody reads the actual documentation before repeating what they were told, and that's going to lead to the spread of factually-incorrect information. It's not a bad thing for people to be aware of the long-term issue with having a WEI API, but users' lack of understanding of WEI in its current form is just going to be used by Google as proof to dismiss dissenting feedback as FUD.