> Obviously, it has to be the same data to make a comparison.
No, it is very much not obvious. There's quite a bit of research showing models, that receive X samples of type A and Y samples on type B might be better in tasks on A, than models that are trained just on X.
When you said "less data", you did not specify the type of data.
> Could it play chess based on a text description of the game?
We don't know - nobody tried it yet. We tried with 320TB text only.
> If we fed a few years worth of video an audio to a neural network, could it write War and Peace?
As Sonny from "I, robot" said, "can you?"