I received the 1511 update for my ASUS T100, but not for my DT.
I waited until yesterday and decided to use the media creation tool.
I had the old one from the original Win 10 install.
I ran that one and after the final settings I checked the version and found it to be on the same version.
I then went to the MS site and downloaded the MCT from there and ran it.
When done I was on the 1511 version.
So my GUESS is that if you are going to use the MCT to upgrade don't use one from the original install get the latest one.