They're not.
Take "This means that AI Overviews generally don't “hallucinate” or make things up in the ways that other LLM products might."
This is just a lie, in two ways:
1. It's still an LLM, feeding search results into the prompts and asking for a summary reduces the probability of hallucination compared to directly asking the question in the prompt, it's still a probability non-negligibly above zero. This kind of pretending you can "fix" the hallucination problem by feeding data into the prompt is extremely wrong and dangerous.
2. It's missing the entire point. "Um akshually the LLM didn't hallucinate, we simply gave it Reddit user Fucksmith's post which it confidently restated as truth" (or indeed, the much funnier, "we gave it The Onion, which it confidently restated as truth") is functionally the same as a hallucination to the end user. The mechanism here does not matter.
These are both fundamental critical issues to AI overviews. "Rare" hallucinations are unacceptable on a tool used billions of times a day. And the LLM paraphrasing lies/satire/ignorance/etc into truth is a fundamental flaw of using LLMs to paraphrase like this.
You can't just patch this issue, the entire thing is fundamentally flawed.