You can run a shift kit to a mathematical match to a side by side comparison of a fixed rear gear. While all the chains, brackets bearings etc are rattling away the direct drive will be further down the road.
Now some one will say but with my gears I can make up for that.
It does not change simple physics. While I run two J shaft creations and love them. I loath for the day I could keep my gears and have just one chain!