Is "topic-comment structure" only used for teaching second language learners Chinese?
The topic-comment structure 主题述语句式 is a linguistics concept. Also referred to as 主题句 and 主题述题句式.
It appears it has been popularized — in the West — by Thompson and Li, Subject and Topic: A new Typology of Language in the '70s. With that paper, the authors introduce the concept of topic-prominent languages 主题突出语言 (Chinese, Korean, Japanese, etc.) vs. subject-prominent language 主语突出语言 (English, neo-latin languages, etc.).
But there are also Chinese scholars who investigated this around the same time. One of them is Zhao Yuanren 赵元任,《汉语口语语法》（A Grammar of Spoken Chinese):

汉语句子里主语和谓语的语法意义是主题 (topic) 和述语 (comment), 而不是施动者 (actor) 和动作 (action)

So it's definitely not a new idea.
Now, it makes sense that grammar is not taught to natives using linguistics concepts.
The notion is however useful to foreigners, and I would say especially speakers of subject-prominent languages, because it pinpoints immediately the most distinctive trait of Chinese. And it does so in a way that can be understood rather easily, as topic-comment structures exist in English and neolatin languages as well, despite not being very common.
Below, some examples I can come up with, which convey that the topic is especially stressed in the sentence (topics in bold):

[English] it was me who called Anna (= I called Anna)
[Portuguese] à estação, esse autocarro não chega (= esse autocarro não chega à estação)
[Italian] il libro, gliel'ho già restituito (= gli ho già restituito il libro)

(I was also not aware of topic-comment in any of the three above, until when I started studying Chinese)