What’s going on with the grading of the 1958 centavo?

Obverse of the 1953 (left) and 1958 (right) centavo coins. 
Note the difference in the level of detail, most notably in the waves of Marti’s hair.

Coin grade distribution for 1953 (blue), 1958 (red) and average 1C (gray) from both NGC (left) and PGCS (right). The average 1C was calculated by adding the population of all 1 centavo dates. Note the bump in 1958 AU coins much higher than 1953 and the average. 

Question 1
Edge view of NGC graded fine reeding (left) and coarse reeding (right) varieties. 
Note the difference in the number of reed in between two prongs.
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