You can't just add lines of code to the boot file, you need to rebuild the entire thing for it to run correctly. The only thing i can think of is the update which was launched had the new boot file with the versus mode added (after doing the update i had the versus trophies added to my list) and this download just unlocks it. So he might not be lying when he said it wasn't on the disc, but at the same time it really is an unlock key.
You can't just add lines of code to the boot file, you need to rebuild the entire thing for it to run correctly. The only thing i can think of is the update which was launched had the new boot file with the versus mode added (after doing the update i had the versus trophies added to my list) and this download just unlocks it. So he might not be lying when he said it wasn't on the disc, but at the same time it really is an unlock key.