I have just checked, and you are wrong, the reference solution contains those strings. I have published an updated version of tests with more explicit assertion messages. The vectors are sorted in the tests before comparison, and for some inputs the logs of failed tests overflow the buffer, but there is nothing I can do with it.

I beleive the Rust expected answers are incorrect. For the value of n = 6, the expected answer does not contain:
"()((())(()))"
"(((())(())))"
Which are both valid answers.