Good point. However, approaching this problem from "YAGNI" point of view is a bit misleading, I think. If you are not going to need the timestamp, you shouldn't add it to your code base.

In my opinion, hastiness is the culprit. When a property appears to be a binary one, we jump to the conclusion to use a boolean way too quickly. We should instead stop and ask ourselves if we are really dealing with a situation that can be reduced to a single bit. The point raised by the article is a good example: you may want to record the state change as timestamp. Moreover, in a lot of the cases, the answer is not even binary. The values for is_published may be, "Yes", "No" or "I don't know" (and then we will be too quick to assign null to "I don't know"). Underlying problem is that we don't spend enough time when modeling our problems. And this is a sure way of accumulating technical debt.