From the article, Google AI is deeply integrated with Google Search. So the article is correct - turning off one turns off the other.

From a privacy perspective, having all of this off by default is sensible. But only offering a basic product like Search if you opt into AI (when search as a capability does not need AI to function) - is newsworthy.

> when search as a capability does not need AI to function

That means a far less capable search engine. Note that Google search has been AI-powered since before AI became a thing; it's now just more advanced, and particularly, explicitly publicized.