The article uses the words "integrated" vs. "internal" shrinking.
> the raison d’être of internal shrinking: it doesn’t matter that we cannot shrink the two generators independently, because we are not shrinking generators! Instead, we just shrink the samples that feed into those generators.
Besides that it seems like falsify has many of the same features like choice of ranges and distributions.
> The key insight of the Hypothesis library is that instead of shrinking generated values, we instead shrink the samples produced by the PRNG.
Hedgehog loses shrink information when you do a monadic bind (Gen a -> (a -> Gen b) -> Gen b). Hypothesis parses values out of the stream of data generated by the PRNG, so when it "binds", you are still just consuming off that stream of random numbers, and you can shrink the stream to shrink the generated values.
Here is a talk that applies the Hypothesis idea to test C++: https://www.youtube.com/watch?v=C6joICx1XMY . Discussion of PBT implementation approaches begins at 6:30.