I think I was inspired by chinese poker (I woke up thinking about the idea, so the beginning of my thought process was kind of lost) but yeah, it somewhat resembles Anaconda for two players.
It just seems to play well with those numbers. Keeping only four makes it possible to keep most of a straight or flush, which makes it possible to reason very specifically about what the opponent might hand over. Passing more cards results in an excess of strong hands, which makes the game less fun to play. In principle one could write a script to check what the probabilities are of one side having an unbeatable set of cards to hold with various numbers of cards held and passed, but I haven't done that, and the question of 'how interesting is it' isn't really well defined.