It is and it isn’t. Again, the whole thing is super vague. Machine vision or pattern seeking algorithms do not try to imitate any human behavior, but they fall under AI.

Let me put it this way: Things that try to imitate human behavior or intelligence are AI, but not all AI is about trying to imitate human behavior or intelligence.

LLMs are one of the approximately one metric crap ton of different technologies that fall under the rather broad umbrella of the field of study that is called AI. The definition for what is and isn’t AI can be pretty vague, but I would argue that LLMs are definitely AI because they exist with the express purpose of imitating human behavior.