Ah, OK. But yes, the impression I’ve gotten from the links so far is these escalators have a far greater radius than those stairs, and so I suspect there’s little extra difficulty walking down them compared to straight ones. Of course, that also removes any of the benefits of a smaller volume needing to be excavated.
Yes and no, there are two escalators at a local train station here in Tokyo, Japan. They rise like a regular escalator then level off before rising again. However, there are no entrances or exits to the sides.