From the documentation, AWB "Changes {{Uncategorised}} to {{Cat improve}} if categories added."

But if there is no {{Uncategorized tag}} (and no categories - such as is common with new articles), and AWB adds categories (e.g. yearxxxx births), it neglects to add {{Cat improve}}.

If the only categories are ones added by AWB, the article should have the {{Cat improve}} tag also regardless of whether there was or was not an {{Uncategorized tag}}.