Hard to tell from the picture, but one possible reason might be this:
One building we installed some dimensional signs to was made of concrete elements with small rocks/gravel/pebbles (don't know the right word) embedded in the fascia. So we had to chisel out the rocks where the holes and pins would go, if the mounting placement interfered with the hard rocks. The shortcut version is to just drill the hole next to the rocks, making the holes randomly askew.
Took a good deal of time to chisel out the rocks since half of them were embedded into the concrete, but we had to do it to make it right. Looks like they did not bother here (if the situation is the same).