I see that we can do a clean install using the same download as the upgrade, but only if we upgrade first.
So its not as bad as it originally looked but is still a waste of time upgrading before clean installing.
"Q: After doing a free upgrade to Windows 10, how do I clean install Windows 10 subsequently?
A: Once your device upgrades to Windows 10 using the free upgrade offer and activates online automatically, you will be able to clean install (i.e. boot from media and install Windows 10) the same edition of Windows 10 that you upgraded to on the same device during and after the free upgrade offer. You will not be required to purchase Windows 10 or go back to your prior down-level version of Windows.
Windows 10 FAQ covers which edition of Windows you'll get upgraded to depending on the edition of Windows 7 or Windows 8.1 that you start from (Refer to the question "What edition of Windows will I get as part of this free upgrade?"). More information on Windows 10 editions was published last month.
To enable clean installation of Windows 10 on devices that upgraded and activated online using the free upgrade offer
You will be able to download and create installation media on a USB drive or DVD for the appropriate Windows 10 Edition
You will be able to skip entering the product key during Windows 10 Setup. Windows 10 will activate online automatically on such devices. The skip option is only available when booting from media and launching setup
The automatic online activation will occur seamlessly after clean installing Windows 10 if the device had previously upgraded and activated online the same Edition of Windows 10. No product keys are required.
Q: What happens if I change the hardware configuration of my Windows 10 device?
A: If the hardware configuration of your Windows 10 device changes significantly (e.g. motherboard change) Windows may require re-activation on the device. This is the same experience as prior versions of Windows (e.g. Windows 7 and Windows 8.1). The free upgrade offer will not apply to activation of Windows 10 in such scenarios where hardware changes reset Activation."