well, yes, exactly. I'm not trying to claim that old code is more reliable just because it was written a long time ago, I'm making the claim that old code is more reliable because of the survivorship bias. If code was first written 20 years ago and is still in production, unchanged, I can be relatively certain there's no stop-the-world bugs in those lines. (this says nothing about how pretty the code is, though).
I was maybe a little unclear with the phrasing, I meant to say "software that's been around for 20 years is more reliable than software that's been around for 2 months"
Yeah this is my mistake, the phrase "can't you just turn it off" was in several drafts but got edited out, and I missed that during the publishing of the essay.