Interesting. The author generalizes quite a bit, and uses terminology that is non-standard (or at least non-US-standard). A few statements are simply incorrect. (e.g. "...the reality is that all pipe tobaccos will have come from the same source and will be graded this way originally." AND "If we look at the table below, we can see a plant position can potentially produce any of the colours - depending on how long the leaf is left on the plant to ripen.")
It's worth noting that the author is from Tanzania. He provides no source for his information, and I would assume that it is specific for Flue-cured tobacco production in East Africa. I think most members of this forum will immediately recognize that the names provided in the graphic for stalk positions differs from anything ever posted here.
All that being said, it does provide an overview of flue-cured tobacco grading in East Africa.
Bob