Yeah, Shimano semi-annoyingly came out with another freehub spline pattern (like they did with the 10-speed-only hubs they briefly had). The cassette with fit on that or on a normal HG-11 driver. The motivation is to have better spline engagement so they can make it out of aluminum (like that one time, with the 10 speed...), but unlike microspline it still has a 11t minimum cog size.