This is because the head for the long valves doesn’t just have the stand higher, it also has the saddle centered farther away from the valve tips.
The shaft bolts and valve stems are on converging lines, so as each gets longer, they get closer together.
Moving the shaft away from the tips is to allow(theoretically) the same length rocker to the used for both heads.
That head for the long valves would have the shaft bolt moved slightly away from from the valves, compared to the other one.
