Think about it this way. Case 1: SRC->TGT (fluent) gives you a grammatically correct text that may have bits that are lost in translation. Misunderstood idioms

Think about it this way. Case 1: SRC->TGT (fluent) gives you a grammatically correct text that may have bits that are lost in translation. Misunderstood idioms and connotations. A reduction in nuance. Case 2: (fluent) SRC->TGT gives you an incorrect text that contains errors of syntax and semantics, that doesn't use natural sentence construction. It'll reads like it was written by someone with less than a perfect grasp on the language, which will be true. They won't be able to accurately convey the meaning because they won't have an accurate grasp of the target language. Also in case 1 you can consult expert quality reference texts to make up for your lack of knowledge in the source language. Not so in case 2.