People have been trying to expose this by getting the AI to do tedious stunts. For example, to count "1, 2, 3..." up to high numbers and the AI "seems" to get annoyed, like a real person.
Suspect? It's already been exposed.
"AI Chatbot Turns Out to Be 700 Engineers in India":
https://tech.co/news/ai-startup-chatbot-revealed-as-human-engineers