Hopefully, someone who has more experience with the archives, or somone from one of the Judging Standards Committees will chime in here and give more details.
But briefly, for one item on a Model A, out of some 5500 parts on the car, there may have been a few, or a dozen or more engineering releases for each of those 5500+ parts. Each of those engineering drawing releases would have to be researched. Not all are actually available, and/or nor can all of them be found in the archives. Also, the dates on those drawings are not always the exact gospel as to when the item was changed on the production line. Those that do take the time to research the archives are not being paid to do so. And it does take a significant amount of time to research just one part.
Both national clubs have Judging Standards committees, and they are made up of volunteers. Consider the amount of hours that represents. A lot!
The Judging Standards get changed in a variety of ways. But, basically, there needs to be a consensus among all of those members for the changes to take place. The changes are based on research done through the archives, as well as research done through the original/unrestored vehicles available for viewing and photographing.
Just take a look at Steve Plucker's research on various parts. There's a good example of how much research is required to thoroughly document a part and all of the changes that occur. Again, this is a hobby, and it takes so much volunteer time to document the changes enough to require the Standards to be changed.
The next revisions, due out soon, have an incredible amount of volunteer time put into them. We will owe the JSC members an enormous Thanks when it is finally available.
OK, now. Time for someone on the JSC to respond and give more details.
Dave Lopes