Today I asked myself why those topics aren’t closed by default. The risk that no one notices someone posted there is quite high because the topic does not appear in /latest. About the General category does not even have a real user as the author, so no one will be notified. But even if someone is the author, the risk that no one will respond is high. There was a question in the about marketplace topic two weeks ago. I’m not sure if someone noticed because usually posts receive reactions or answers.
So maybe closing the topic would be the better default. Most new about topics here at meta are closed. If someone wants discussion in there, they could still open the topic.