A number of reports on the web this morning have claimed that Windows 10 build 10061 is being offered to some Windows Insiders who installed build 10056. This isn't the first time something like this has happened, so I think it's time to explain why this actually happens and why it usually doesn't matter.
Firstly, build 10061 is only being offered to those who installed a leaked build, not an official one. The official builds and the leaked builds are tweaked ever so slightly, which make Windows Update behave differently. Official builds are tweaked to look for 'low' flight risk builds, whereas the leaked builds are tweaked to look for 'medium' flight risk builds.
Insiders usually only ever get access to builds marked as low risk unless Microsoft make an exception, meaning medium and high are generally for internal employees running on the Microsoft internal network, and sometimes close partners. There's no way to download these medium and high risk builds as they require authentication with the internal Microsoft server, and rather obviously the majority of normal Windows Insiders are not Microsoft Employees / Partners and therefore are unable to download.
So if you're running a leaked build and see Windows Update failing to install a newer build, it doesn't matter. The build it's trying to download is something you'll most likely never be able to get hold of, unless Microsoft make an exception or lower the flight risk of said build.