- They found a task that GPT wasn't very good at, because examples of that task weren't in the training set (in any language).
- They trained a fine-tuned variant of GPT where examples of the task were in an appended training set, but only in English.
- They told the variant to do that task again, in other languages.
- Its performance improved on all of them, not just English
If the training set has no Mandarin examples of the task, how did it get better when you ask it in Mandarin? Sure, you could fake this by having an API call to Google Translate where it takes the Mandarin request, translates to English, solves the task in English, then Google Translates back to Mandarin. But it's not doing that, it's just doing the same "predict the next token" operation on the Mandarin prompt.
I don't see how it can do that unless it really has some kind of understanding.