Also in terms of a second being a second, yes, presumably if you took a pocket watch back to the beginning of the universe, it would not operate observably slow

Also in terms of a second being a second, yes, presumably if you took a pocket watch back to the beginning of the universe, it would not operate observably slower. Imagine you had an inter-dimensional being that could traverse spacetime at will. They have 2 stopwatches, one is in their left hand at the center of the universe 12bn years ago, the other is in their right hand at the edge of the universe today. If they started both stopwatches at the same time, the one in their left hand would take longer to reach 5 seconds than the one in their right hand.