Earlier quoted context omitted.
That is interesting. In many English speaking cultures children will informally refear to their mother's parents and father's parents by different names even if formally they are both "grandmother", "grandfather" or "grandparent". I like that in China they formalised the names.
Even "Uncle". In english, Mom's brother and Dad's brother both are uncles ¯\_(ツ)_/¯
You can have a mother-in-law, a brother-in-law, a son-in-law, but there's no such thing as an uncle-in-law.