The author didn't mean that an older commit date on a file makes code better.
The author is talking about the maturity of a project. Likewise, as AI technologies become more mature we will have more tools to use them in a safer and more reliable way.
I've seen too many old projects that are not by any means better no matter how much they get updates because management define priorities. I'm not alone in saying I've been in a few projects where the backlog is rather large. When your development is driven by marketing people trying to pump up sales, all the "non critical" bugs begin to stack up.
The author is talking about the maturity of a project. Likewise, as AI technologies become more mature we will have more tools to use them in a safer and more reliable way.