there was a youtuber who distributed kind of messed up cias of this hack, did you get it from a youtube channel? wouldn't be surprised if they ended up on certain forums or collections.
it's also possible these prepatched cias only work for citra, because you can definitely not use any other format than fat32 on a 3ds and no matter what you do with the file, if it's larger than 4gb you can't put it onto fat32 in a useable format.
you might be better of installing a normal ultra sun/moon and using the respective layerd fs files from
https://gbatemp.net/threads/pokemon-nightmare-moon-and-reaper-sun-new-thread-new-leader.499525/