Maybe it doesn't work in sysnand because it's not properly encrypted, or a part of it was not signed.
hmm nothing is decrypted, so, everything should be encrypted ok and signed ok
oh yeah i updated the op - someone told me their gba ambassador games did work fine in sysnand.
when i first was told about this method it seemed that yes, everything would work in sysnand. i'm not so sure about that, but, i heard their gba games worked, so, maybe somethings will work ok in sysnand (most? all? - i don't think all)