Comment by lblume

In that case we read it entirely differently — the last paragraph explicitly mentions inferring "Nullable fields that never hold nulls are often the result of incomplete migrations or forgotten cleanup steps". The author also proposes a script "to identify cases where the field could safely be changed to non-nullable". But alas, we cannot do that with full generality, due to there being a big difference in intent that cannot be captured purely by counting nulls, and surely not by only calculating percentages.