Clean install Windows 10 and then using Windows 7/8.1 serial

According to this article (http://news.softpedia.com/news/windows-10-creators-update-can-be-activated-with-windows-7-and-8-1-product-keys-514679.shtm), I am able to use my windows 7 pro OEM key on a clean install Windows 10.

I guess my question is: do I need to have upgraded my windows 7 to 10 previously? Or I can just go from activated Windows 7 pro to a clean install (and activated) Windows 10?

Thanks a lot.

The license code from previous Windows should be fine for Windows 10. But you may need to make some changes to the installation media to install proper version, as you must use the same version as it was (Home/Pro). To do that you may need to edit (create) file \sources\ei.cfg and put this there:

[EditionID]
Professional
[Channel]
Retail