This is wrong. The latest released version of Windows 10 1511 build 10586.11 allows direct fresh install of Windows 10 and subsequent activation with a Windows 7 or 8 key of the same type (home or pro). I have done it twice.
This was introduced in insider preview build 10565 a couple of months ago but has been on general release since 10586 a couple of weeks ago.
Google will find lots of links about this e.g. this quote:
"Also, starting from Windows 10 1511 Build 10586, users will be able to clean install and activate Windows 10 using their Windows 7, Windows 8 and Windows 8.1 product keys."
from:
http://www.redmondpie.com/windows-1...vember-update-is-out-heres-how-to-update-now/
Last edited: Nov 22, 2015