I got the 105 disc groupset which had the same description, and it's just a normal mount on the rear derailleur. I wonder if it's referring to the front derailleur, which is braze-on.
It's referring to the rear derailleur which is direct mount but they always come with the extra hanger knuckle as standard.
@joeae started
London Fixed Gear and Single-Speed is a community of fixed gear and single-speed cyclists.
I got the 105 disc groupset which had the same description, and it's just a normal mount on the rear derailleur. I wonder if it's referring to the front derailleur, which is braze-on.