__FUNCSIG__ with MSVC for variadic template

If I run the following code with MSVC ...

#include <iostream>

using namespace std;

struct S {};

template<typename ... Args>
void variadic( Args &&... args )
{
    cout << __FUNCSIG__ << endl;
}

int main()
{
    S s;
    variadic( (S &)s, (S const &)s, (S &&)s, (S const &&)s );
}

... the code prints (re-formatted) ...

void variadic<struct S&,const struct S&,struct S,const struct S>(
    struct S &,const struct S &,struct S &&,const struct S &&)

Why has the parameter-list the proper reference-types I specified while calling variadic and the specialization inside <> doesn't have the proper types for r-value references ?