I think fluency in the target language is more important for the reasons PhasmaFelis and igravious say. Or to put it more bluntly, because understanding is generally an easier task than speaking/writing.
For example with my level of English (a lowish C2), I can understand all kinds of texts, including literary texts (I read lots of novels), but there is no way I can write English at a literary level. I would tell the facts of the story just fine, but the special "feeling" that good writers give to the text would be lost.
Curiously, this notion (that the best translator is one who is native or 100% fluent in the target language) is widely accepted in Western cultures, but someone told me that in China is the other way around. When they hire Chinese to English translators, they especially value their knowledge of Chinese, not English. Which may partially explain the "Engrish" phenomenon...
Well, if I wanted a Chinese text explained to me, I'd rather have a native Chinese explain it to me than somebody who is fluent in my own language and studied Chinese.
I see it all the time with translations from English to Russian. Because I know English better than most translators, I can spot all sorts of mistakes. I'm pretty sure a native English speaker, even with mediocre proficiency in Russian wouldn't have made those mistakes.
For example with my level of English (a lowish C2), I can understand all kinds of texts, including literary texts (I read lots of novels), but there is no way I can write English at a literary level. I would tell the facts of the story just fine, but the special "feeling" that good writers give to the text would be lost.
Curiously, this notion (that the best translator is one who is native or 100% fluent in the target language) is widely accepted in Western cultures, but someone told me that in China is the other way around. When they hire Chinese to English translators, they especially value their knowledge of Chinese, not English. Which may partially explain the "Engrish" phenomenon...