This was used to prepare for upgrade to win 10 ,so why are some win 10 users now being prompted to download it.

It updates C:/Windows/System32/appraiser - this contains files related to hardware/software compatibility and enables
it to evaluate your system and determine its compatibility for future ugrades to windows 10.

So they want to update that information.Probably why someone like me who is currently running 1511 and blocking 1607
has been prompted to download it.

I wonder if in the future they are going to use this to force people to install 1607?