The log cabin hitbox covers all of the corners of the tiles it touches, or at least appears to.
Regardless, when I turn grid on, the place my character walks toward is not in the center of the tile, so this thing spawned very close to the smelter because that can happen, apparently.
This should be fixed in that they should follow the same rules as items. Already on my list, but a bit harder to fix.
"The psychological trials of dwellers in the last times will be equal to the physical trials of the martyrs. In order to face these trials we must be living in a different world."