It doesn't look like they cleanly slice into 16x16 tiles. What I mean is that when setting up tiling for grassy areas, the grass bleeds over into the tiles for stone/dirt and that breaks auto-tiling bit masks. Well, not exactly 'breaks', but it ends up looking bad because there are grass elements in tiles that are not surface tiles, so their bit mask can lead to those tiles being selected for placement where it doesn't make sense. The area of the grass tiles from the first green pixel at the top to the lowest green pixel of grass at the bottom of a particular grass tile, is not actually 16 pixels os it doesn't slice cleanly into a grid.
But I could just be doing it wrong, so there's that.