Yes. A meta-analysis of 17 randomized trials found that rehearsing social situations in simulation reduced anxiety roughly as well as facing them in real life. Strong evidence that practiced reps transfer to the real world, even when the practice is not 'real.'
The obvious objection to practicing conversations is that it is not the real thing. The research undercuts that worry. When people rehearsed feared social situations in a simulated environment, their real-world anxiety dropped about as much as it did for people who did in-person exposure.
Your nervous system does not require perfect realism to update. It requires repetition of the trigger in a safe setting. That is what makes out-loud, real-time practice with a lifelike coach more than a warm-up: it is exposure your brain counts.