Not sure which Knuth paper you're referring to but skimming through the article my understanding is this algorithm works /only/ if the values are hashable. IOW how else does one define unique/distinct values ?
Looks like it was posted at the time https://news.ycombinator.com/item?id=36079213 but not much discussed. I found it over here https://news.ycombinator.com/item?id=40387594
note how "u"s are selected every time value is not in a list. I don't read it as being a hash.