It seems like because there's just so much of it that people just haven't got to the "meta puzzles" yet.

I'm 20 hours in and starting to see examples of mechanics being generalised in a way I wasn't expecting, i.e. an early games thing turns out works in a way more general way that elevates the mechanic in complexity and feels like a very satisfying moment.

I have a suspicion about another that would completely change my perception of the game if it turns out to be true, so... meta puzzles? Not sure, but certainly there's something more than just the 4 initial rulesets colliding.