I think this is an EXTREMELY important point, one we sometimes overlook when talking about the TPGs.
A grader in the 1990's could put a bit more value on luster, ignoring a few minor bagmarks or dings away from the fields. OTOH, a grader in 2022 could value luster a bit less and focus on bagmarks and dings.
As all of us know, and Roger always posts here, grading is subjective. Standards change over time (maybe unfortunately)...but so do graders (inevitably, as people change jobs or retire).
Most of the coins I collect or study are larger coins, Saints and Morgans and other gold/silver pieces. So I like to read stories or anectdotal discussions about how dealers and graders and collectors value these coins over time. For instance, right now, Carson City Morgans are super-hot....any raw coins submitted are catching the TPGs at a good time. Maybe you get a bit of leeway and get that extra 1/2 to 1 point grade boost based on specific factors that your grader(s) just happened to "like" that day.