thank you so much for your informative posting.
It does seem to be a grey area, how very odd.
I would say that if one can’t undertand the other,
it’s a language.
Chinese writing is ideogram, one Chinese character has different pronunciations in different ares, but the meaning is same. This is the secret why Chinese can read text wrote in ancient, character’s pronunciation always changes in the past thousands years, but the meaning is almost dateless.
Two people from distant areas even can’t understand each a single pronunciation, but give them a pen and a paper, they can have conversation without ANY barriers.
Don’t be mislead by stupid people, it’s very very different from Indo-European languages.