If by "good for the figure" we mean support of the body in good shape - then any descent along the escalator will be beneficial. If you want to enhance the positive result, go down with a heavy backpack behind your back i.e. by simply artificially increasing your weight.
Absolutely any daily physical activity brings great benefits to the figure, it's not so much in a specific way as in duration.
Go down the escalator along which other people go up. Considering the speed of the escalator and the size of the steps, this would be a very good warm-up before escaping from the guards)