It is a name mismatch. Steam frigates, which have black hulls and steam on their pictures and a vertical line on their NATO symbols, come 1 to a unit. Regular frigates come 2 to a unit.
About the Jackson thing, I think I mentioned this on that thread too; it is a game quirk that the leader sprite stays with the unit after he dies, but Confederate divisions were named for their commanding general. I guess since Jackson kicked so much rump they decided to keep his name

just as the Stonewall Brigade did even after Jackson was given corps command.