Some other thoughts:
- Analysis is limited to results of individual battles. That's a very narrow slice of a general's actual job.
- He ties WAR to overall W/L, which isn't great but the data doesn't give you many options.
- The model rewards "underdog" wins. This sounds like a decent proxy for skill, but it seems like a big part of the job is avoiding being an underdog in the first place.
- Army size and casualty figures for anything pre-17th century (and that's generous) are extremely suspect.
I wouldn't trust this model to compare Montgomery to Patton during the Sicily invasion, let alone compare Caesar to Napoleon.
As someone who picked up a computational military modeling course in college, attempting to model ancient warfar is a vastly different task than modern battles.
My gut would be that modern warfare de-correlates more strongly from numeric advantage due to increased speed and lethality of available force types.
Also, for the author, if you wanted to be more accurate, start calculating actual expected outcomes from the forces. Lanchester's Laws are as good a place as any to start.