Then why does anyone bother getting it set if its only going to change again? The idea is to slacken the adjustment bolts off, adjust it to what you want, then tighten them back up again, the only way the numbers will change is if the toe/camber/caster adjustment hasnt been tightened back up.
Laser alignment is done with the car and wheels on the floor so the figures are what are going to see once you drive off, isnt it?
I definitely agree with the second part though, thats like a Kebab house not using pitta bread or elephant leg.
Of course you will get slightly different readings as there is so much flex in the suspension mountings that you will never get the same readings twice. The differences will be minimum however a difference none the less.
Alex