I couldn't tell you why Shimano did it that way, but as far as I'm aware, the 107 is symmetrical, 53.5/53.5, and so is the 113, 56.5/56.5, but the 110.5 is asymmetrical, presumably 56.5/54.0(?)
The 110.5 spindle gave a 47.5 chainline and the 113 gave a 50.0. With the way they designed fms in...