The article has absolutely nothing to do with "hashes vs. PRNGs". Literally nothing. It's all about the linear algebra and floating point operations that happen (in this case) to be used to transform those numbers. It has nothing to do with PRNGs.

Also, PRNG and hash functions are extremely similar, and there's no reason why one should be deterministic and the other not. They're both built out of simple integer and bit operations. If a certain PRNG is implementation-defined, that's a detail of the specific (possibly standard) library you've chosen; it's nothing fundamental.