I've noticed that the same page tool is promoted a lot by people here. I'm in no way shape or form saying that this is a bad thing; I personally find it very useful myself and I have never had a game where I've run a successful session 0 fall apart due to disputes among the party. However, that said, I've noticed that the one website is promoted a lot here, and I would like to know whether it's just that everyone really finds it useful or if there's any official endorsement by the staff here thus leading to this level of popularity.
There is no official endorsement or relationship going on.
The Same Page Tool's author was formerly a member of this community. They shared it here, several members found it quite useful and also shared it in other contexts, and it's frequently relevant to a certain type of social issue (expectation mismatch) which we run into a lot.
Members promoting it are doing so for their own reasons (such as because they feel it's useful); there's no ulterior motive there. If you see it promoted here more than elsewhere, that's just because there's been some powerful hearsay about it here.
Speaking as one of the people who mentions it fairly frequently, I have no formal relationship with bankuei - it was just an epiphany moment when I first saw it and contextualized some previous RPG-related issues I'd had through that lens, and I'm guessing the same is true for others.
Note that the Same Page Tool itself is not actually a great answer for most questions; it covers a limited set of variables. It's more the idea that people should agree in advance on what game they're playing if at all possible.