Don't be too sure about that. [0]
I've talked to a lawyer about how they handle this. They do indeed double-check everything, since it'd be embarrassing (or worse) to send hallucinated statements to opposing council or to the court. They still find the assembly a huge time saver
But based on stories in the news on the subject, not everyone has this same level of diligence
You can get an effectively-zero hallucination rate with the right setup already.