I'm going to say that there is variation on this particular detail. I have run into off-white or beige daubs on the rim tire surface (read hidden by the mounted tire). Those were superb condition original dry climate wheels. That daub is likely either an inspection mark or a quick visual identification mark, either of which could have random placement by various workers.
Not challenging the daub being on the backside near the weight area (I have seen that also), just offering other observations.
Not challenging the daub being on the backside near the weight area (I have seen that also), just offering other observations.