"Security Update for Windows (KB4056892) is already installed on this computer."
That suggests it is installed but not applied.
Heh. I wonder if there is a typo in this workaround. This is actually one of the issues that this patch is supposed to be fixing
https://support.microsoft.com/en-us/help/4056892/windows-10-update-kb4056892
<quote>
Windows Update History reports that KB4054517 failed to install because of Error 0x80070643.
</quote>
If that is the case you don't have anything to worry about and you should not see it offered again.
Unfortunately they deleted the original workaround but fortunately we have a copy of the original
FYI
Robert