Possible engine related issue with placement on tile edges

Have you ever tried to fill a tile surrounded by cobblestone with 9 saplings and realized you can't place it on some edges?

Or tried to place 5x5 grid placed grass/twigs?

I am almost certain that this is not an issue with Geometric Placement. The placement marks you see here are not offset from the origin, but you can't place anything directly on the x and z axis of a tile if the adjacent tile is blocked.