Not precisely. The issue at hand isn't just that Google displayed the AI summary, but that they authored it, making them responsible for its contents. If the defamatory content had been in a snippet in the search results, they would've been fine, because that clearly has another author who can be held responsible. The AI summary has no other author than Google; therefore, they're responsible for what it says.

(What's the alternative, after all? Having no one responsible for what the AI summary says is clearly untenable.)