AIUI doing what you said would permit the network request to proceed, and it would fail because nothing is listening on port 80  We already know that the phone-home bails out when there's no network connection, so perhaps that code also bails out on connection failure?
Alternatively, is there some way to make DNS lookup itself fail for ocsp.apple.com?
Last resort, if we know how to fake the response, running a dummy server listening on localhost would be faster than allowing the request to go over the internet.
 Empirically, `curl http://0.0.0.0` yields a connection failure. I think I know that 0.0.0.0 is used in a listening context to mean "listen on all interfaces" but tbh I don't really know what it means in a sending context. Maybe someone can educate me?
Right, and as far as we know that exception might be caught in the same way as "your computer doesn't have any network connection at all" is caught. Or would those be likely to generate the same exception? Either way, there's a chance that it would result in exec gracefully and quickly not doing the blocking phone-home isn't there?