SCALDING MILK
When making a custard (which serves as the base for this ice cream recipe), it is necessary to scald the milk. This accomplishes two things: it dissolves the sugar, and when whisked into eggs it increases their temperature slowly and helps prevent curdling.
To scald milk, simply place a medium saucepan over medium heat. Add milk, stir occasionally, and watch for steam and little bubbles to appear around the edges of the pan. Do not let the milk boil. Remove the pan from the heat and proceed with your recipe.
This doesn’t really makes sense. When you scald the milk, you either have to let it cool down first, or you have to temper the eggs in order to make sure the eggs don’t curdle. The only reason eggs curdle is if you heat them up too quickly. And the only reason that would happen is if you mix them with hot milk!
If you mixed them with room temperature milk and heated them up, they wouldn’t curdle.
So while you can prevent curdling while using hot milk (by tempering), to say that scalding the milk helps to prevent curdling is nonsensical. You can prevent curdling despite scalding the milk, but if you didn’t scald the milk, you wouldn’t need to prevent it.
There are other arguments for scalding the milk, but preventing curdling isn’t one of them.