I tryed with my retail cartridge(rev00)(SN:AQEP510192) and i get the same, save non corrupted but blank.
Yup, I suppose now we'll wait for OP to update the save
then this is already a sky3ds save file, there's nothing for me to convert here
did OP ever post a fixed GW format save file for EU, just like the one that is still available for US?
He mentioned that he was working on it, so no not yet afaik