Easiest reason is the 'introduction particle', blub which we don't have in English, for subordinate clauses.
I think 'taught ChatGPT to invent a' is hyperbolic though, this is more like 'taught ChatGPT my invented' - the only thing it invents itself are the 'relex' word->word mappings.
I agree the author/experimenter seems to have done most of the conlanging here. The development benefit comes, I think, from having the AI reflect back the work so the experimenter can correct output and consider their conlanging decisions (eg use vowels for case marking).
