"My understanding is that casinos must operate on a gold standard, where they have actually money to back up each and every chip they produce."

Not true.
A NV casinos bankroll kept on hand is a very complicated formula including how many table games, slots, progressive jackpots, keno limits, sports book limits, chip float, etc, etc, etc.

Once there is a reasonable expectation chips will not be returned, the bean counters take over.