Polynomial Time Reduction - Does 0 calls to the black box still imply a reduction?
Yes. As you note, $f(n) = \sum_{i=0}^{k}0\cdot n^{i} = 0$ is a perfectly valid polynomial in $n$ (for every fixed $k$).

What you have left over without the oracle calls is just a polynomial time algorithm. This observation also underlies the fact that any polynomial-time solvable problem has a polynomial-time reduction to any other non-trivial problem.