Maybe I am not explaining it clearly enough what i am trying to say but the difference is not the illusion it is a fact of time dilation between two objects, the illusion is that we made the clock run slower, As I understand it we have not made anything run slower we have just changed it's position in space-time relative to the other clock and if both clocks had observers tied to each they would have measured both clocks always ticked to the same decay rate just not relative to each other in space-time so the clock never slowed down (the speed it travelled through time at, speed c)