After looking at the late-1500 character IDs, I might have an idea on why Jo is that far down the list.
Most of the cards in that range are in the expected order of first come first serve, and event releases like Mou having the ID based on the initial release (February 14th) rather than the NB release (March 3rd). With that logic, Jo should have been roughly 1648.
Four exceptions to above. One is Cannibal Jo; other three are Bapho Ld, Predtr Ld and Rekt Ld.
Purely a guess, but based on the card ID and the "shy and fearful girl who finds herself surrounded by a gang of criminals" part from the Arcade SB2 blurb, I think she was meant to be the third new LD from that season, but the plans changed and she was re-purposed as a comic release.