It appears that the installer is needed for Server Manager - so should I install WSUS in the future its ready and up to date.
No. No. No. That update *IS* the WSUS BINARIES. You CANNOT "install" that update.
You can approve it, but it will stay NotInstalled for all of eternity until you DO choose to install the WSUS role on a WS2008R2SP1 server, and THEN the WUA will download the bits from the WSUS server.
And your servers will continue to be 99.9% Installed until that day. (This is the significance of the words "Dynamic Installer" in the update title.)
Someday when you have a few hours to kill, read ALL of that thread; during the course of the thread I describe about a half-dozen times that the update will never install UNTIL the WSUS Role is selected for installation.
