Not having a copy of 10 yet, I was going by some tech blogs stating it in the same way I put it. One can assume they kept it for some reason...perhaps for enterprise customers and those with IE based whatevers...apps etc..
But it seems clear to me that the intent is to totally replace it, due to it’s gross weight, with a new lighter, faster build.
Yup. enterprise, business, legacy users. Eventually it WILL go away, probably just wither and die on it’s own.