I believe the claim that hidim is steganography comes from the title of hackernews link. The site itself claims to represent torrents as .png, but not to disguise them.
The claim that this will frustrate search engines is true, in the sense that no one is looking for this format at the moment; obfuscating with an awkward format is a short term dodge.
It seems to me that the likelihood of a real search engine adding special image analysis on crawl, just for this, is vanishingly small.
Not to mention you can also insert these PNGs into other images, too - like sig images, as the page suggests.
People can pick away at it all they want, but the fact remains that it's a huge innovation in distributing torrents without running the risk of coming up in search when Interested Parties google the torrent name. And it works great now for this purpose.
Nothing on this earth is guaranteed to work forever, so that's hardly a damning flaw.
The claim that this will frustrate search engines is true, in the sense that no one is looking for this format at the moment; obfuscating with an awkward format is a short term dodge.