Which Groupset?

Ah I found the info here

There’s a road specific 12 speed freehub currently only available on DA wheels

Most importantly, the new cassettes fit both the new 12-speed specific road freehub (that currently only exists on Dura-Ace wheels) and are compatible with existing 11-speed freehub bodies (which I guess makes them 11/12-speed freehub bodies). The thickness of the cogs and spacing between them also remains the same. Shimano told me that there was always extra room in the existing freehub design for the 12th cog, especially with the larger cassette cogs being able to be cantilever further toward the spokes.