At endgame, Ansem gives a speech about how Riku, in his desire to leave the islands, ended up causing grave consequences for both himself and his homeland. However, in light of Birth by Sleep and 3D setting up Young Master Xehanort as Riku's Evil Counterpart (... maybe), right down to hailing from the Destiny Islands and having the same motivation to escape that prison, as well as revealing that Ansem (or rather, Xehanort's Heartless) had a direct hand in Young Xehanort's Start of Darkness, it wouldn't be out of character for this line to also be making a mockery of Xehanort's younger incarnation.
Ansem: Look at this tiny place. To the heart seeking freedom, this island is a prison, surrounded by water. And so, this boy sought to escape his prison, and he opened his heart to darkness.