This is because the tree is placed in the middle of the grid. Not sure if it is intentional though, if the maker thought it was something cool. Also noticed it myself back when I did the mission.
It’s not a bug, it’s a feature. In random map generation for competitive play this would be a problem, but this is scenario and it is showing you that it is possible to place items off-grid (ctrl + G to change placement behavior in the editor I believe). Mark this post as solution if this satisfies you.
Edit: how did you zoom SO much? what’s your resolution at?