I tried translating the article "Metabolism" from English to Yoruba using SX. This is a new article, so SX suggested translating the opening section. This includes the navigation box, which is the {{Biochemistry sidebar}} template in the English Wikipedia. It did it string by string: "Part of a series on", "Biochemistry", "Chemistry of life", "Index", "Outline", "History", as if each of these things was a sentence in the prose.
I also tried translating "John McCain", and it tried to translate strings in the Infobox ({{Infobox officeholder}}).
Section Translation shouldn't try to translate these templates at all. At best, it should try to adapt the template (T275374), and if it can't be done, it should just be silently skipped. This ticket proposes to hide block templates until they are properly supported. In this, users won't waste their time translating pieces of rendered content of templates that have no effect in the published article.
For the creation of new articles (promoted by the new entry point in T286645) template such as infoboxes are quite common. So the issue may become quite visible.