Wow, this is one of the cleverest ideas I've seen in a long time.
As far as I can tell, they've put together a wide-ranging set of fairly generic-sounding movie music (generic = good, so it doesn't call attention to itself)... but composed it in a way that the three parameters (momentum, depth, power) simply map to different volume levels of the underlying instrumental tracks -- but all perfectly tuned to always produce a pleasing result.
As far as I can tell raising a slider often maps non-linearly to more volume, but sometimes it reduces/removes instruments too.
So there doesn't appear to be any machine learning, nothing crazy fancy -- which is what makes it so clever and impressive in a "I-wish-I'd-thought-of-that" way. I can only imagine the amount of product iteration it took to arrive at what the 3 parameters should be (and why 3 instead of 2 or 10). It reminds me a lot of Adobe's Multiple Masters technology for typefaces. [1]
If they keep putting out enough of these master tracks, I wonder if it will reduce the market for film composers. After all, most films don't need recognizable motifs, they just need music to tell us how to feel, and this meets that need perfectly. Bad for music students, good for film students...
[1] https://en.wikipedia.org/wiki/Multiple_master_fonts