>>3856370"Containment board" does not just mean "thing that is bad" or "thing that I don't like".
It refers to something very specific, that being topics that are not permitted to overlap with other boards.
So for instance, if you have a case of a video game that has an anime adaptation or vice versa, you will be permitted the video game adaptation of the anime on /v/ or the anime adaptation of the video game on /a/. This is a case where the topic is permitted on both boards.
However, the same can't be said about My Little Pony. You'd be allowed to talk about a My Little Pony video game on /mlp/, however, you would not be allowed to talk about it on /v/. This is because /mlp/ is a containment board.
While [s4s] does heavily emphasize shitposting, the board does not have any actual topic, and thus it is not "containing" anything. It's just a statement that the content quality standards are lower than other boards. Same goes for /b/.
The only containment boards on 4chan are /pol/, /vg/, /vp/, and /mlp/. You *might* be able to argue that /r/ counts as well since recommendation threads are b& on several boards, but that's really up in the air.
Consider yourself educated.