I have problems understanding your point here. What was announced was not a new operating system but a translation layer built into Windows 10 that translates Linux system calls to their Windows counterparts.

I also bet many people would disagree with your statement that W10 is unusable and worthless without this feature.

The Windows kernel always existed and has evolved over the years: NT, 2000, XP, Vista, 7, 8, 10. They didn't develop it as the "last missing piece of the puzzle".