The laser alignment tool should be adjusted for wheel runout before measurement starts. The tool is usually attached to the wheel rim at three points, so an initial reading is taken with each 'leg' at the bottom, rotating the wheel a third of a turn each time. A mid-position can then be set as a datum.
I'd hope this is done, and may well not be noticed by an observer, but may be worth watching closely, or asking how they account for an untrue rim.
I have watched. No account of runout taken. As with anything. Its down to the quality of the staff and time allowed for the job.
My previous car had alloy wheels with between .5-1mm runout on all four wheels.
worse case all the errors add up. Best case they cancel each other out. Most of the time it will be somewhere in between.