Waymo itself is clear that it has no remote driving capability whatsoever. The Waymo driver is in your vehicle, so any technical issue (e.g. phone network drops out, satellite fails, whatever) won't affect the vehicle's self-driving. It may give up and pull over and let you out, but since it's local any situation where the driver is disabled would be similar impact to a human driver - if a block of concrete drops off an overbridge and smashes the Waymo driver, that could easily happen to your Uber driver the same.

Hence their choice to employ humans to attend in person and drive a Waymo which gets into trouble. In fact the humans sometimes have had to "chase" a Waymo car that, unless it has been specifically told to stop, assumes it should try to complete the journey once it can figure out how. Waymo's remote support can reach into the driver's model and tweak it e.g. to label a stray traffic cone as just trash, not actually off limits - but they aren't driving the car.