I very much doubt that that's a typographical error; the game generally sticks to US Navy hull classification symbols when it needs to shorten ship classifications, DD is that system's standard symbol for destroyers, there isn't a "Light Destroyer" classification unless you count something like the Destroyer Escort (hull symbol DE; during the Second World War, generally a ship somewhat smaller and slower than the fleet destroyers and primarily intended for convoy escort, broadly similar to the contemporary frigates of the Royal Navy), and DL is already taken for "Destroyer Leader" (generally speaking, a ship intended to lead formations of destroyers, often though not always an oversized destroyer or a small cruiser and usually having space for command facilities not normally found on "regular" destroyers) or, from roughly the 1950s to the mid-1970s, "Frigate" (at the time, a fleet escort larger than a destroyer but smaller than a cruiser in the US Navy's classification system).
