How to call a constructor without argument could advise the use of braces

In 2-ObjectProgramming/3-constructors-destructor.ipynb#[WARNING]-How-to-call-a-constructor-without-argument, we could advise to use braces:

#include <iostream>

{
    Vector v{}; // Constructor Vector()
    std::cout << v.norm() << std::endl;
}

and

#include <iostream>

{
    Vector v{5., 6., -4.2}; // The other constructor Vector(double x, double y, double z)
    std::cout << v.norm() << std::endl;
}