But regardless, having had to deal with some legacy code written 10 years ago by someone who isn’t working at the company anymore, I would take an outdated spec over none at all. At least then I know what people intended back then, what they cared about, what they had and hadn’t considered. As long as the spec is written by a human, that information is surely valuable.

I see your point, and I think I would partially agree. I guess that, to me, specs need to be more of a live document than something someone writes and gets forgotten over time. I still think that thoroughly commenting code and having a strong E2E test suite is a better option overall.