What it actually does [0] is set group policy according to the Microsoft specified methods [1]. It would have helped in this situation as not only would Windows not have downloaded the update in the first place, it would have deleted it had it already been somehow downloaded.

[0]: https://www.grc.com/never10/details.htm

[1]: https://support.microsoft.com/en-us/kb/3080351

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You can check the technical details https://www.grc.com/never10/details.htm

It basically does what Microsoft would do in order to keep Windows from upgrading.