One rebuilder quotes that in a certain percentage of rebuilds he cannot maintain the original 60/40, but for some he can rebuild but has to settle for 50/50.
Then we should probably define what it "should be" and what you are likely to get.
It "should be" 60/40.
Mine had 10/10. (that would be 50/50 but with virtually no resistance at all)
Now they all have more/less. (meaning I don't know if it is 60/40 but it is definitely different in opposite directions)
Why most can't get the 60/40 split is because the valving attenuators in the chamber fence is very hard to rebuild. Most would probably not bother with them and leave them at 50/50, and most drivers wouldn't notice the difference anyway.