I think you're right about the reason for scribing the location, for almost any "service procedure", I can tell you a couple steps that are entirely unnecessary (drain the coolant, then remove the lower radiator hose... the second tends to take care of the first
).
From what I've seen, GM has some of the best struts overall. Look up the camber/caster procedure for a Windstar if you doubt that
. All Fords have the same rediculous "slot the strut mount holes", but for the Windstar you have to remove all the plastic over the struts. I'd like to see those strut towers after a few alignments, might be better to drill out the holes to 1/2"
I can do the camber in about 5 minutes on each side on GM struts (once the vehicle is set up on the rack). What I do first, while it's still on my hoist, is put my impact on both bolts and spin the them so the splines chew out the metal, leave them just snug and then drive it over to the alignment rack. The machine we have has "jacking compensation" which means you can raise the wheels of either or both axles just off the turn plates and you can easily move the camber to exactly where you want it, and the computer compares the before and after jacking angles so it tells you exactly the angle (to .1 degrees) even with the wheels jacked. Once I have the camber where I want it, I have a helper snug the bolts while I'm still holding the wheel in the right place (or if nobody has any time to help, I'll just leave the top bolt snug and tap the wheel with a plastic hammer). The reason they have the bottom hole slotted on the repalcement strut is that any time you replace struts you need to align it, the slot just makes it easier to do it properly. It can be much further off with the slots if you do it the quick way, but every replacement strut alters the alignment a few tenths of a degree which usually makes the car dirve a bit off. I have seen some that the camber and caster are both off but cancel eachother's tendancy to pull. After replacing suspension components, I'd say less than 20% are even within the tolerance range, and even half of the tolerance can make it pull quite a bit depending on what's off and in which direction.