In your vote to close you can indicate where you think the post should be migrated. In processing that vote, diamond mods can select any site for migration and usually follow suggestions (because we're grateful for the thought that went into them in the first place).
The system limits how many sites can appear as targets for redirection. I recall we are at our limit and believe the existing ones (SO and Math) are targeted far more frequently than DS. Indeed, even if we had the room, DS wouldn't be high on the list. This year we have migrated posts to Econ, OpenData, GIS, Signal Processing, and even English at least as frequently as to DS.
BTW, in this case I elected to keep the question open because it does require some understanding of the underlying algorithms and therefore, it seemed to me, is not solely a question of computing--but I have to agree that it might be more suited to DS. I tend to defer to the OP's choice of site in such cases and therefore do not immediately vote to migrate.