I agree with the first one perhaps. The last two are deliberately spelled that way I presume.
I think they used unique spelling to add to the in-game culture and atmosphere, but that's just me.
In either case, Final Fantasy is a pretty big budget series and so I'm sure they wouldn't miss too many genuine mistakes before they published it, without there being a good reason for them.
However, you do still come across a few, especially in the earlier games. FFVII has some real classics

.