i vaguely remember a project that was developing a file from hash application, the idea was to use an provided hash, and an arbitrary file to accompany a generated padding file that would be packed in so the whole torrent matched the hash.

at about the same time there was a practice of a running padfile, that you would ammend every time you retorrented so that the hash would change and make it hard to kludge out the distribution network by tracking known hashes.

in summary it think it is very possible to "forge" hash numbers and impersonate or obfusicate the content

hash collision is rare, intentional hash mimicry maybe is not so rare.