This. They probably simply used an “image similarity” algorithm, of which many are readily available and do not require much computing power. The credit at the bottom of the website for “Chroma”, a startup with no live product and hiring, suggests this could be a growth hack. Like “let’s ride the buzz of the moment with a barely useful tool quick to develop, hit front page of HN, and get some visibility.” Good for them, it worked, but yeah the product is probably bogus as you’ve demonstrated.