The highly random and somewhat convoluted mechanisms remind me of something like character creation in the rpg classic traveller.

You do have a little choice there (unlike here), but I think the same appeal is present even without the choice.

The experience is a bit like reading fortunes from tea leaves.

The fun comes from assigning meaning to the outcomes. This happens, generally, automatically as a human instinct. In traveller, the process of character creation generates a kind of narrative in your head of who the character is.

I've been thinking about these kind of experiences a lot lately.

Is it a game? I don't think a discussion of definitions is very interesting, but I would call it a game by any casual meaning of the word. Certainty, in traveller's case, a roleplaying game. But I recognize the same appeal in these zero-player games.

You're playing something, just in your own mind. The primary game isn't what's on the table, but what's in your mind. You're not committing to choices in physical (or digital) space, you have no agency there -- but there's still a rich experience happening between your ears -- full of hopes, predictions, disappointments, elation, creativity. It's like reading but you're also part author. You're not reading from a book, but from pattern matching inside randomness.

I'm still trying to wrap my head around it myself. I have little more than the recognition of something interesting in this direction, but beyond that I can't articulate it.