You're the one who's extrapolated that the rule asks you to assume ignorance. The post, and the Recurse Center guidelines it's built on top of, don't make that claim.

If I say it's a social guideline to not tell somebody about something wrong with their outfit unless they can fix it in under 5 minutes, I'm not suggesting you go around assuming that everybody knows they have a stain on their shirt. I'm telling you it's net-negative to point it out to them.