If I understand correctly, the problem is that Japanese Wikipedia abuse filter number 13 triggers a warning in Content translation.
It seems (based on what I understood form automatic translation) that filter 13 is intended to warn about short articles being created. Content translation tries to check early the contents against abuse filters for each paragraph in order to surface issues as early as possible and be able to tell where the problems are. This approach is beneficial in many cases, for example the source article may have a youtube link which is ok with the source wiki but is prevented in the target one. By warning early and showing the specific paragraph we can help the user know where to look for such link and fix it. However, some abuse filters expect to evaluate the whole article, and checking just a paragraph can result in a false positive. In your case, the filter considers that the evaluated text is too short for an article, but it was actually just a paragraph. Unfortunately, the edit filter infrastructure does not allow to differentiate both kinds of filters.
I'll bring this to discuss with the team again to see if there is something actionable we can do. to improve the situation.