not understand front and rear (like the Z32) alignment geometry. As said they rely 100% on what the machine reads. How many check tire pressure and make sure both are even? Do they load the car for they way you mostly drive it? How many check the rims for lateral runout? How many understand the meaning of the toe, camber and caster spec ranges on alignment and set the middle of the spec when adjustable, all that I have witnessed, not the way. I do not trust Align shops unless the operator can successfully answer my questions, most can't.
From the race days I usually do my own alignments with simple tools and it is right on.