When you have a job to do, you have to do it even if you don't know what you're doing. In this case, the editor knew they had to finish the film, yet they didn't know any Chinese. Rather than move to China, learn Chinese, and then come back to finish the job, they just went for it. I actually really like how upfront and honest they are. They could have tried to guess what the guy was saying, but that wouldn't be fair to literally put words in the guy's mouth. At least this way we feel a little more connected to the editor.
The thing about subtitles is you can't really trust them if you don't know the language. Who wrote the subtitles? I had a friend who wrote subtitles and he was just some stoner. He didn't care about the job. You could be watching a foreign film subtitled by some twenty year old stoner.