> I disagree with my sibling comment. The trick is beautiful. If you generate UUIDs such that each bit in the result can be reliably traced back to a single bit in the input, then you can take a substring of the UUID and use that to infer which bits of the input integer must be set to produce that substring.

...but that has nothing to do with what the website is doing. The accompanying article specifically calls out the fact that it can't be done while maintaining the appearance of an unordered list, and therefore it isn't attempted.