They can have access to everything, if you use GBoard (default Android keyboard app).

Of course the headline is misleading. AI has always read your messages, if you allowed it. It depends how the AI is used and if it respects your privacy. It is possible and you can enjoy having your messages classified (or tagged) properly, so you know what are ads, which one belong banking, news or things you're interested in.

As long as it assists you to do some boring complex tasks, it can be a great help.