Ehhhh....not really. If that were the case he wouldn't have given a !@#$ about looting methods or burning food. Instead we were hamstrung for ages, restricted to looting tax gold and stealing food. We would have won the southern war much faster if we'd been plundering Aenilia's lands the whole time, for example.
Because you mistake the means for an end. One of Jenred's "ends" is island-wide rules of warfare that are more restrictive than even the Order of the Hawk envisioned. The problem is that he has multiple ends, most of which support each other in the endgame, but getting to all of the ends is...Difficult.
I think you also underestimate how badly Zonasa, Aenilia, and Kindara could have hurt Arcaea if they stopped dicking around in Larmebsi and went for the western regions looting with a vengeance.