-
The bigger biggest cog gives it more room as all the spokes have started heading inwards towards the hub more, so mtb 11 speed overhangs the back of the freehub a bit instead of sitting flush like road stuff and needing more freehub length, 11 speed spacing is the same across the board. In practice some smaller big cogs could overhang like the mtb stuff and therefor fit on an 8/9/10 freehub, so some people machine them to fit on some hubs, and now some of the wider range cassettes fit out the box.
Just read that you can use 11sp R7000 cassette on a 10sp wheel. How does that work? I thought the 11sp spacing between cogs was narrower than 10sp. Does that mean Dura-ace R9000/9100 and Ultegra R8000 aren't going to be compatible with R7000?