[AkibaSilver]

Trying to make a coherant Dalk timeline, even just out of their TV appearances, is an exercise in futility. The old BBC Cult Website for the explanation was that the Daleks in "The Daleks" were the left-behind remnants of the full Dalek race, early prototypes dependent on static power, and the Thals have their story wrong from centuries of knowledge drift, but the real explanation is that audiences wouldn't be expected to remember an unrepeated, decade old story at that point, and Terry Nation didn't want to be beholden to an off-the-cuff bit of lore he'd already contradicted himself in his 60's Daleks comics to restrict his stories.