Why cant partial methods be public if the implementation is in the same assembly?

According to MSDN Documentation for partial classes :

Partial methods are implicitly private

So you can have this

// Definition in file1.cs
partial void Method1();

// Implementation in file2.cs
partial void Method1()
{
  // method body
}

But you can't have this

// Definition in file1.cs
public partial void Method1();

// Implementation in file2.cs
public partial void Method1()
{
  // method body
}

But why is this? Is there some reason the compiler can't handle public partial methods?