But "expresses the same idea" isn't the benchmark, "ideas expressed in the same way" is the benchmark.

A translated work is "ideas expressed in the same way", a translation doesn't change that.

See e.g. this question/top answer on stackexchange, it details pretty well how plot can't be copyrighted using Harry Potter as an example: https://writing.stackexchange.com/questions/3928/on-copyrigh...