He’s talking about unnatural (non-idiomatic) language. That’s not an issue you can fix with better grammar; there are many language learners who possess good intonation and pronunciation, and natural (idiomatic) speech, but poor grammar: their idiomatic speech more than makes up for grammatical mistakes.
Source: learning languages for 10+, have met students as described above.
I interacted a bit with the AI and the Portuguese is fine, it's just that it conjugates, uses the proper pronouns, etc. These things a typical Brazilian does not do.
The difference between standard Portuguese and oral language in Brazil is enormous.
This reminds me of a story from my Russian teacher. She was speaking with some American Russian-speakers who work for our three-letter agencies or something, and their Russian was perfect, amazing - but one thing gave them away: conjugating numbers too perfectly.
Native speakers are lazy: even though they know perfectly well how to conjugate the numbers, it’s easier to rephrase things so you don’t have to.
