They do give a hint:

"This includes making Gemini 1.5 more efficient to train and serve, with a new Mixture-of-Experts (MoE) architecture."

One thing you could do with MoE is giving each expert different subsets of the input tokens. And that would definitely do what they claim here: it would allow search. You want to find where someone said "the password is X" in a 50 hour audio file, this would be perfect.

If your question is "what is the first AND last thing person X said" ... it's going to suck badly. Anything that requires taking 2 things into account that aren't right next to eachother is just not going to work.