Article seems like an ad for Comp Cams. I don't think the cam companies will give out their cam profile data, if they did you could calculate the P-V clearance too.
Knowing engine stroke and rod ratio, you can calculate the position of the piston movement from TDC for any degree of rotation.
Knowing the cam profile, cam installed position, and rocker arm ratio, the valve lift can be calculated at any degree of rotation.
The valve drop test just fills in the missing part (of equation) of how far the valve is from the piston at TDC.
I guess it is a nice service from Comp, and they may even suggest a custom ground cam (less overlap, less duration, or slower intake ramp rate / quicker exhaust ramp rate?) for engines with limited P-V clearance?
If you have the cam on hand, you could check lift at each degree of rotation and have decent cam profile data to do the calculations, but installing it and measuring is easier and more accurate.
In general: More duration = less P-V clearance, More Overlap (tight LSA) = less P-V clearance, Advancing cam install position = Less intake / More exhaust P-V clearance, The reverse for retarding install position = More intake / Less exhaust P-V clearance.