You missed a key point.
"Cortana, Microsoft's digital assistant, is also being developed. Added in build 17063 is support for Spotify, so you can play specific tracks, and ask what is playing, through voice input."
That is a knee jerk reaction, not progression.
They ceased Groove with little warning
They announced partnership with Spotify
Cortana music search feature stopped working and remains so except for insiders.
They now search Spotify