As mentioned, conflict really doesn’t come up that often for a tour guide. Which means it’s not something they can practice on a regular basis.
When you’re dealing with confrontation, there are a lot of things to consider all at once.
There’s obviously something that needs your immediate attention, but while you’re trying to decide the best way to defuse the situation, you’re also aware of your other guests- who are waiting to see how you’ll react.
And perhaps you’re also aware of the fact that you’ve never been in this exact situation.
A very human reaction to this much pressure is to freeze or go into fight or flight (where your instincts take over). What role-playing teaches is that instinct.
Role-playing allows for you to be put in the worst-case-scenario.
So when scenario pops up on an actual tour, you’ve been here before (theoretically). And you can allow your body to go into auto-pilot, using the techniques & wording that you’ve practiced during role-playing training.