I'm not saying who is right or wrong. Mike seems to consider the load comes only from the spring. So higher lift equals more load.
I don't know how much the inertial forces are compared to the load from the spring but they must count for something.
These forces would come at the moment of highest acceleration (at or near valve opening) and are influenced by the mass of the objects being accelerated (weight of the valve assembly). Conversely, as the valve reaches the point on the cam lobe where the acceleration starts to slow, the inertia of the already acccelerated mass starts to take load away from the rocker tip negating spring pressure felt at the tip. This counter force would be greatest at or near the end of opening and the begining of closing or the point that the spring pressure is at it's highest. Again I don't know the quantity of that force (dependent on the mass and acceleration rate) and how it compares to the force from spring pressure.
But what if for arguments sake it is more than the spring pressure at the seat. This could mean that the load on the rocker is higher at beginning lift and lower at max lift.