I think this is a good idea for a site like this focused around searching for things because if you're going here to look up "revive" you're already expecting a

I think this is a good idea for a site like this focused around searching for things because if you're going here to look up "revive" you're already expecting a search result not necessarily expecting to find a precise "revive" out of the gate. Adding this to the rest of the site or for other non-search focused sites showing something the user didn't ask for just because it's similar could be a lot worse experience than signaling "not found!". Especially for how rare a plain incorrect URL is a problem vs an expired resource.