Windows 10 Build 10565 was released last week to Fast Ring users. It was the fourth public build since release, and it contained the most listed changes of any of them. One major change is the ability to clean install Windows 10 with a Windows 7 or 8.x key. Previously, users would need to install their old OS and then upgrade it. This was particularly annoying for users who upgraded an old version of Windows to 10, did a reinstall of Windows 10 for some reason, and the activation servers didn't recognize them. The official solution in that case was to uninstall Windows 10, installed Windows 7 or 8.x again, then upgrade again. (Again, this is only if a Windows 10 reinstall failed to reactivate for some reason.)
Tonight, the bandages come off… or on. On. Definitely on.
That's last week's news, though. This week, they moved Build 10565 to Slow Ring and released ISOs for it. The interesting part is that Slow Ring users, until now, were still on the official build, 10240, alongside the general public. This is almost too close to the rumored November update of Windows 10 to be worth it. At the same time, they also chose the build with some of the more severe known issues to flight to the Slow users, such as the inability to use Search without Cortana. This makes me wonder if they pushed it just to release ISOs for the above reinstall with Windows 7/8.x key feature.
If you're a Slow Ring user that is still on 10240, then this is your last chance to disable Insider builds, if you are properly activated.