From the article and then reading the wiki on Miranda, it seems that the moon used to be in an irregular orbit which would magnify the tidal stresses, but is not anymore, so it was presumed there was refreezing as the heat reduced. But with this paper perhaps not yet enough freezing far enough down to make the ice break as expected for a solid layer. I would guess that from the point of reaching any water below, Miranda's layer will be far more difficult than ones like Europa and Enceladus, or at least until we learn more.