Trust me on this one...

You play craps but, you have a crap game. (no plural, not a craps game)

You shoot seven after establishing a point, you crap out.

But on the chip it refers to the Crap Game. You don't play at the Craps table or Craps game.

Can I trust an English dictionary, explaining a French word from Louisana USA? LOL I can cite other industry usage without the "s" if you need it.

But since the original question was "is this an error", I'm sticking with my answer. No, it's not a mistake, joke, or error.