While you're conceptually right, in practice I think it bears mentioning that in C# the two syntaxes compile differently. This is because C#’s target platform, the .NET Framework, has always had a function called `string.Format` that lets you write this:

  var str = string.Format("{0} is {1} years old.", name, age);

When interpolated strings were introduced later, it was natural to have them compile to this instead of concatenation.