Just noticed this, they don’t always use the entrances/exits, but go through the wall instead.
Maybe they are ghosts? 
Could be. I tried to get a closer shot as a villager went through and this was the result. Must have caught him right when he was in the wall because can’t see him at all.
Got one this time.
Less a wall and more a boundary, though.
News for you all, villagers and Traders all go through boundaries as if they don’t exist, but put a road in the area and they’ll use that.
Did the wall just finish being built? There was another post on fences that finish being built after the character had already determined its path to walk on so after moving them again later, they would not walk through the fence. I think graveyards though don’t have fences as separate entities, but rather just a visual. They behave like buildings, allowing entry in all directions technically but preference from certain points. When I put several 3x3 graveyards side by side, and later was able to build the crypt on them, I noticed that I could place them anywhere even if it crosses a wall between joining 3x3 grave yards. So it would seem the wall is purely visual.
No, the graveyard had been up for some years as it was one of the first things I needed to build. 