From my limited understanding of Mandarin, the Power Reserve does not work like a PR should (where the older ugly version he was comparing to does work).
What i think it does based on the video, is like a 24h time indicator - it moves as the time moves (goes back and forth pendulum-style). It reaches the end (48h) when the hands cross 12 midnight and then goes backwards returning to the top of (12h), and then down towards (48h) again.
Guy in video said you have to accept this minor flaw amidst the rest of the good work, as to get a working PR would have cost more or was not feasible with the rest of the design priorities.
It was also mentioned at the start that this is the first great iteration of the 5712 and there might be modifications to it in future (timestamp 3:19)
But the dial is indeed pretty awesome to look at and very tempting just for looks.