Anyone can learn how to say 你好are you? But seriously, getting basic taxi cab mandarin down in 6 months is pretty easy. Heck, when I did it it was much harder since real beijingers back then had thick 儿 accents.

You definitely don't need 大山-level mandarin to do business in china these days.

You're just going by intuition, which can be misleading.

Guangdong province alone is 100 million people. Some of whom are Mandarin speakers (1st or 2nd or 2nd+ language). But many are not, not even as 2nd or 2nd+ language speakers. And their predominant language is Cantonese. Many people grew up before mandatory Mandarin education was instituted. There's a similar situation in other huge provinces all around China, especially southern China.

Tibetan parts of Sichuan have many non-mandarin speakers, though these are technically a part of greater Tibet anyways.

Wrong. A lot of people grew up before this started. And no, I removed the Mandarin-as-an-additional-language people from the number already. (Mandarin 1st + Mandarin as a 2nd or 3rd languages speakers) = 1.1 billion. Population of China, 1.4 billion. 1.4 billion minus 1.1 billion is 300 million.

I’ve run into old people in China who don’t speak a word of mandarin, especially in Tibetan areas. They get the kids to translate for them.