While I agree with you, as I understand the SQL standard defines the N in varchar(N) as characters (not bytes). There is a pathological case which is not commo

While I agree with you, as I understand the SQL standard defines the N in varchar(N) as characters (not bytes). There is a pathological case which is not common: max length of all 4-byte characters. Indexes are used to enforce features like unique constraints, it's important that everything can fit in the buffer length.