I think Jim is right about changing machine payout percentages while you are playing.

However, remember that slot chips with several different percentage payouts can be approved and available to the casino. If the server has a slot chip with lower payout available to it, I'm assuming the casino can swap to the game percentage on that chip whenever they want, subject to the time restrictions applying to a current player. They have always been able to do that, but it took a tech to swap the chips inside the physical machine. This just makes that an electrical swap, not a physical one, and doesn't take the machine out of play for the swap time.

I don't look at this as a "conspiracy" to fool the players, at least in Nevada. When done in another state or juristiction, there is certainly the potential for making changes an inappropriate times. It depends on the technical smarts and supervision of the gaming authority.