I don't know what the early version of the textbook is like. I know that earlier high school textbooks taught more contents, including calculus. Later, the curriculum reform wanted to reduce the burden, so the content of integral was deleted, leaving some knowledge points such as limit and derivative.

School is the last edition of textbooks before the curriculum reform. That version of the textbook is the version after deleting some points before.

So your statement is not accurate enough, it should be a little calculus, but now it has been deleted, leaving only limits and derivatives.