For me, this did not contain Skullsplitter. It contained Zepetl's Short Sword, the same one as here. I am sure I saved the file correctly, since my chest had previously contained a full Lucreti's Stars set. I am also sure that I didn't accidentally overwrite the Skullsplitter file with the Short Sword file, since I had never downloaded the Short Sword file until after the Skullsplitter file didn't work (in order to check if you had accidentally reversed them - you didn't, Zepetl's works fine.)
I was able to successfully create a Skullsplitter though, using an item editor. Skullsplitter is named "unique_axe_2h_spalter", item ID 2475, item type 2466.