Why ref and out are not sufficient to disambiguate overloaded in C#?

Question

For example, why this method Max(ref int x, ref int y) is not considered overload of Max(int x, int y)? Why is the same with out?

Answer 1

public void Max(int x, int y)          
//No Error
public void Max(ref int x, ref int y)  
//No Error
public void Max(out int x, out int y)  
//cannot define an overloaded method that differs only on parameter modifiers 'out' and 'ref'

First and second method can be overloaded. But the second and third method cannot be overloaded because both ref and out are treated differently at run time but they are treated the same at compile time.