[Closi]

Their explanation seems fine to me, if a little awkward.

> We don't flip over the yellow card because nothing tells us that a yellow card needs a circle on the other side. Not because it is yellow and we know that the circle is on the other side, because we don't know.

If a card is yellow, it doesn't matter what is on the other side, so we don't have to check it. Either it is a circle, in which case the rule is upheld, or it is any other shape, in which the rule is still upheld.

In the case of the red card, it DOES matter what is on the other side, as if it is a circle the rule is broken.