Unfortunately it seems that the old stock is running out and they're now selling robots with a firmware version that is too new for that rooting method right from the factory. _Some_ users report that they still got UART rootable robots but the number of those who didn't steadily increases.

That doesn't mean that those robots aren't rootable though. We do have more rooting methods, however those aren't public currently. It is TBD how we will move on from here.