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Whether a hash function is cryptographic or not is irrelevant: either way, it's computable, therefore you can reverse it and get information about the original data you hashed. Because that data was only weakly random, it's not independent of future data from the same sources, so you can compute what future results of the hashing algorithm are likely to be.

Obviously this is impractical in the real world, but in TCS randomness is defined as algorithmic randomness, which completely ignores the question of running time. Randomness is a mathematical concept, something can't suddenly become non-random because you gained a faster computer. For more information see: https://en.wikipedia.org/wiki/Kolmogorov_complexity#Kolmogor...

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To correct that: there are many different definitions of randomness, and they're not actually using a form of algorithmic randomness in this paper (there are many definitions of that too), which I guess isn't so relevant for randomness extraction.