I would have expected a larger announcement for a release like this. It seems to come from Apple's acquisition of Turi in mid-2016 [0]. From what I can tell, they are open sourcing most of that product with new integrations to Core ML.
Will be interesting to see how Apple plans to position this against existing ML solutions with easy to use Python api's like scikit-learn, keras, etc.
[0] https://techcrunch.com/2016/08/05/apple-acquires-turi-a-mach...