Slimelung weirdness

[Slvrsrfr]

I was doing some casual map scouting and noticed that Slimelung appears to stretch into the map side borders. In a weird way, this crop is from the same pic in my main thread. Any map would show it, I suppose. But, I find it peculiar that the generator places swamp biomes the way it does. It seems to leave it's 'footprint', even though the biome is not present. And that neutroium can be infected with it. I didn't know that. Also, none of the other biomes seem to leave any sort of signature on the fringes. Maybe something in the algorithm is awry?