Direct Connection ( Mullen LA ) heads

"Why Lift beyond the peak flow of a head"
Its area.
Lets picture a cam lobe ..'a soft triangle' for the purpose of this example. Open close...the higher the lift-the wider apart each side= the more time in peak flow and just a blip at peak lift where it may or may not back up or saturate..or even momentarily dip and come back.

"Why beat the **** outa the valvetrain"
Who says you have to?
Thats on the lobe profile/designer of the cam.
Classic magazine 'everyone knows example' -- Hughes engines.
High velocity lobes .