I thought in my case it was greyed out because some time ago I had relocated the /Library/Audio and /Library/Application Support/Logic folders to an external drive and pointed to them with symbolic links. That's been working fine (as long as I remember to have the drive mounted, of course).
I only looked after thinking I might put everything back where it belongs and relocate what it will with this new functionality.
Anyway, I just noticed that hovering over the greyed out menu item yields this info:
Funny, everything works, and the Sound Library Manager shows everything installed. 😕