Properties of Hadamard Manifold

Question

Since we know that $\mathbb{H}^{2} \times \mathbb{H}^{2}$ is Hadamard manifold. It is written in the paper " Equidistance surface of the bidisc" that $\textbf{Every sphere bounds a ball that is strictly convex}$. Can someone explains me whether it is property of Hadamard manifold or it is some theorem about Hadamard manifold.