The technology they are discovering is called "Language". It was designed to encode emotions by a sender and invoke emotions in the reader. The emotions a reader gets from LLM are still coming from the language
Emotion is mainly encoded in tone and body language. It is somewhat difficult to transport emotion using words. I don't think you can guess my current emotional state while I am writing this, but if you'd see my face it would be easy for you.
Emotional signals are more than just text though, there is a reason tone and body language is so important for understanding what someone says. Sarcasm and so on doesn't work well without it.