Problem is GG - I sor'ta like Kitchen Boquet.
To leave it out for me is to leave out something I like.
Put it in if you like, but you wouldn't need it for color if you cook the onions until they are rich and dark colored. Merely a suggestion to try in the future because it makes a big difference in the taste of the soup. The dark caramelized onions are the key to FOS. Give it a shot. You can still use your KB if you want.
In fact, google "key to good FOS" and I'd bet that 9 times out of 10 or so, you'll see the dark onions as the key. All other articles would probably say the beef stock, but honestly, if the onions are done well and there are plenty of them, packaged stock works well.
I was just commenting in general on the various liquors I've used. It wasn't a criticism of what you used.