The blind spot
What no detector was checking
While the detectors disagreed about classifiying the origin of the text a separate test ran on meaning. The same source passage, roughly 1,900 characters of financial writing, went through both tools and every checkable claim was compared against the original.
Fourteen facts: the return figure, the market capitalization, the price target, four named entities, three dates, two more numbers. The pattern-rewriting skill kept all fourteen. The translation chain kept thirteen, and changed three things about what the text asserts.
This is structural, not bad luck. After step one the chain never sees the original again. Each hop rewrites the previous hop's output, so errors compound and no stage has the information needed to notice. By step four the English is four translations from the source.
The pattern-rewriting skill avoids this for one reason: the source stays in context, and its process explicitly asks, before the final draft, whether any fact, name, number, date, quote or citation was added or lost. That question is only answerable if the original is still there.
Both tools cleaned up the surface tells equally well. Both removed every em dash and every curly quote. The difference showed up only where no detector looks.