Why use a public method in an internal class?

There is a lot of code in one of our projects that looks like this:

internal static class Extensions
{
    public static string AddFoo(this string s)
    {
        if (s == null)
        {
            return "Foo";
        }

        return $({s}Foo);
    }
}

Is there any explicit reason to do this other than “it is easier to make the type public later?”

I suspect it only matters in very strange edge cases (reflection in Silverlight) or not at all.