I don't believe I've ever heard anyone end that game with a comment other than "simon says simon says is over" or "simon says is over" or something clear and deliberate to that effect.
Its sneaky, but I have way less of a problem with what you are asking about than most of the ridiculous orders I hear and tactics of delivering them that are used to weed Ts out. These are including, but not limited to: talking as fast as the micro machines guy and not repeating because "No one was talking over me, so you should have heard it" and making things either complicated or convoluted to the extent that its difficult to figure out in time, or perform in time, resulting in being shot. A lot of times, people have only seconds left on the timer to comply and a handful of wardens do that deliberately so someone might miss a beat figuring out what "shift walk out of your cell in a direction the opposite of forwards and do a one thousand and eighty degree turn counterclockwise by 5:04 and freeze" means when the warden finishes saying it at 5:06.
Once you know you are in a game of simon says, you should know that you aren't doing ANYTHING without hearing those two words first. Orders given in this game are identical to warden orders in that they are to be followed else you'll be shot, however, warden orders not including a simon says prefix are not valid (like text commands) until the game is over, signaled by a statement by the warden that the game has ended. He\she must make a statement that is clear and obvious to inform the Ts that he no longer is bound by a conveyance rule (simon says prefix) while whittling down their numbers.
Remember, Jail server rules, keep it fair. I think telling them to 'have fun' during simon says is.