Wait... ds games are written in lua? Certainly this isn't an interpreter, rather than compiled code?!
That said, you may have found code that was in memory and just written to fill up the data on the cart. I'd be surprised if that's still a thing, but this is how large portions of the Link's Awakening DX carts source was released. The code was in memory and when the compiler built the rom, the "empty" data areas contained the ASM source. I can only assume that's what happened here.
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