You can see that if you project NY and Rh Island Aves to the north and east they cross the line of N Capitol Street at N Street (from Scott Cr) and parallel to the top of the triangle in the map.
Penn and Mass Aves cross the 32 line at N Street and parallel to the top of the triangle.
Extending Penn and NY Aves establishes the corners of the triangle and another grid line, south of the CB location.
Looking at a topo map shows that the position on the straight line fell on the side of a steep hill, and the planners didn't have the time to landscape the whole area there.
The CB being located north of the corner of the triangle places both the Jeff Mml and Maryland Ave north of the position and lines determined by the grid.