IO Port can't go in top or bottom of crafter multiblock in MC 1.12?

[mycroftjr]

Why were https://github.com/TechReborn/RebornStorage/blob/1.12/src/main/java/me/modmuss50/rebornstorage/tiles/TileMultiCrafter.java#L51 and https://github.com/TechReborn/RebornStorage/blob/1.12/src/main/java/me/modmuss50/rebornstorage/tiles/TileMultiCrafter.java#L58 made to prevent the IO Port from being in the top or bottom face of the crafter multiblock in MC 1.12? In fact, why are the top and bottom even handled any differently than the other 4 sides?