Translation:We are not Chinese.
I first check the entire sentence 我们不是中国人, but I didn't get anything because forvo thinks it is all one word and doesn't happen to have this sentence.
I separate with spaces like this so that it looks for "We" "are not" "Chinese":
我们 不是 中国人
and listen here:
Then I can click on one of the phrases "Chinese" or 中国人 to listen to four different voices (three from China and one from Hong Kong): https://forvo.com/word/%E4%B8%AD%E5%9B%BD%E4%BA%BA/#zh
The point is that it is correct to use “we”. I have never seen them not accept that. I would report the other one if it did not accept “we”. It would be unusual to find “we all”. Perhaps if people thought that only some of us are..., but the minute you say “we are” that includes only people who are, so it already means all of us. Otherwise, we would have to say “ Some of us are...”
I think that it was more likely “you all” that you had seen. That is a specific form found in the South of the U.S.A. which had been reported sentence by sentence as also correct. It is also seen as “y’all”. If you see “we all” again, take a screenshot and report it.
There are a few people who speak perfectly well Chinese, without accent, but are not Chinese. For instance children of foreigners who were born in China, people who have a tonal language as mother tongue and think tones are easy as pie, and well, even some people who don't have a tonal mother tongue who just mastered the language extremely well.