hmm I got rejected with the same answer and it has been a month, could any mods confirm if there is any reason for this answer not to be accepted
Many people would indeed say "only has" in this sentence, but "has only" is better, as it brings the modifying adverb closer to the noun being modified.
To put the matter another way, "has only" sounds more educated and elegant; "only has" is what the common person would say.
For what it's worth, I used "has only" here and "only has" in a very similar sentence, because I wanted to see if either one would fail. Happily, both were accepted. Of course, maybe one of the translations is missing for one of the sentences...