Well, if you think about it, being able to morph an input text into the voice of someone is the job that some voice actors do, and the task of doing such a thing is something that I would define as intelligent.

In any case, it's not you or me who define the AI term, in CompSci AI is used to mention recommendation systems (which include search engines that do smart ranking, which nowadays is all of them), translation systems, NLP (chatbots, spam filters), Image processing (auto labelling stuff, object tracking, ...) and so forth.

Most of these systems weren't considered "ai powered" before neural networks and deep learning (high layered neural networks), but nowadays most of those are: NLP uses NNs that convert words / text to vectors to then operate around those and decide on stuff (this includes search and translation), Image processing uses NNs too to be able to "learn" information about several images, to then be able to recognize humans, faces, track objects, generate fake images from an input, deepfakes...

Usually, they are called intelligent systems and thus AI because of the way they are prepared, all of those require that some sort of NN is trained with some dataset to then generate a model with weights that is then fed to the NN alongside some input to archieve the desired result. That trained model, which is a bunch of numbers that decide how the input is transofrmed according to the NN, is the, so to say, "intelligence" that the machine as artificially learnt.

That's it, that's literally it, disregard marketing and articles written by salespeople, AI is a system that uses some sort of model trained with a dataset, Usually a NN model although in my opinion, any model (random forests for example) should work too, but it's true that NN models process data of higher complexity.