I don't see what the big deal is...
Im in the same sort of business but work with machinery rather than cars.. You'd be surprized how many small differences there are and running changes. I would Hope that Subaru has far less of these changes than the machinery industry.
Information about the VIN/Serial number along with the parts I obtain are recorded by the manufactuer. WHat if people all over the country were replacing a specific part on a specific range or batch of machines/cars whatever. that may help the manufactuer identify a larger issue. I'm not sure if Subaru does this.
HOWEVER. the parts people should be astute enough to identify the common parts, and if nothing else, create lists or spreadsheets denoting interchangibilty. even for a new guy to take notes of things as he finds them while looking up a part for someone using their VIN.