This does not logically follow. If your bot is getting slammed by a page returning all zeros (what the person I replied to reacted to), all you know is something on the server is returning a neverending stream of zeros. A symlink to /dev/zero is an easy way of doing that, but knowing the server is serving up a neverending stream of zeros by no means tells you whether the server is running in a decently isolated environment or not.

Even if you knew it was done with a symlink you don't know that - these days odds are it'd run in a container or vm, and so having access to /dev/zero means very little.