Title isn't quite fair (also HN auto deleted the "These"), this is specifically about older versions of applications that Apple considered important enough that

Title isn't quite fair (also HN auto deleted the "These"), this is specifically about older versions of applications that Apple considered important enough that some system compatibility shims (sometimes very small) were worth having to keep them working at some level. They're not necessarily unusually buggy, and they certainly aren't the only ones, they're just a snapshot of ones somebody at Apple considered devoting specific BC effort too despite company policy generally being dead against that. It is interesting to see what they are though, and that even Apple is not at all fully immune to the need to keep some stuff working longer over upgrades even if developers don't.