[RET_COP]

Think about how much clearance .010 actually is.With all the different metals involved that someone could mix and match, Heads, Block, different valve stems, different gas temperatures It has to be there for some insurance that the valve will close. There selling cams for alot of different engine combination's.
Ask the question, Why is there No valve lash with hydraulics?
The above problems don't apply.
After knowing how the metals in your personal engine move at operating temps, you could then set your own lash tighter (more causes problems)than recommendations. It changes the cam profile, but if you could grind you own cams profiles to your engine you could keep tighter lashes and have the same profile as the off the shelf one that worked.
Lou