I understand the concerns as well as the lack of concern for changing something that can and will likely be changed in the field. Understanding that in architectural work in residential homes, finishes are seldom specified on plans unless there is some specific reason they have to be. Homeowners and contractors too often change things like GWB thickness and add wainscote and a whole host of other things that we don't anticipate.
In reality a drawing with 1/2" GWB plotted at 1/4"=1' will be so insignificantly small as it would be nigh impossible to distinguish between 1/2" and 5/8" anyway ...
We draw sans finishes on all walls, mainly because we dimension to the edge of the walls .. it makes for more accurate wall placement when there is a close tolerance on clearances.
All of our walls are drawn at 3 1/2 and 5 1/2 with no exterior finishes applied either, this has been pretty standard regardless of who I have worked for .. although occasionally someone would use 4 and 6 because they are easy round numbers to deal with.
Now I have to take issue with one thing posted earlier, because it is true only to a point .. this is merely to clarify the issue ... If your drawing units are inches (most common architectural work) and you draw a 400 mile square, that isn't 400 units ... that is 400*5280*12 or 25344000 units .... this is why some people (namely architypes and surveyors) have issue with using one anothers drawings ... scale up the drawing by 12 .. scale down the drawing by 12 .. adnauseum
So Craig, if the drawings you receive are not to your scale, I would suggest asking the originator what units they are using for the drawing .. also, if you are talking about houses and such, knowing that exterior doors are typically 36" wide and walls are 4" or 6" (nominal width), you should be able to scale an exterior door to 36" wide, check the thickness of the wall and if it is something weird, then use the two to come up with a best estimate. Also, it might be useful to put a few dimensions on the plan you get so you can verify that they make some kind of sense .. like a standard tub is usually 5'-0" long. Given the usual suspected dimensions, (and making sure that you don't have some whacked out exterior dimensions like 49'-3 5/8") you should be fine.