War Spoil Dynamics
Most kingdoms avoid the use of WS because the fear of having no incoming acres with army out can be hazardous when the plan isn't thought through. The upside is the acres can't be ambushed and in the case of dwarves can be built immediately at no cost.
These dynamics can be useful both in and out of war depending on the clearance the WS is used. We have to be mindful of watering down tpa/wpa but otherwise, with solid interference runs, we can increase our economy. The not so big secret is to cast WS after a couple of taps so you have army with acres coming in at the same time as the WS tap. You have to account for outside kingdoms jumping into wars as a precaution.
Dwarves can do this easily, but a wealthy kingdom can also, with accelerated build and army training. A good candidate might be dryads who have the military capability to ensure healthy taps and already have a training bonus. dryads have passive land efficiency from their food bonus. Faery have the defense and generally have a good trade balance to benefit as well. Dark elves have converted elites they might protect.
When do these strategies come into play? I've used WS tactics when I was alone in a shell kingdom as a human war hero. The number of randoms I encountered offered an understanding of attack rhythm; yes feel. Essentially out of war you have an ops ceiling that some kingdoms are reluctant to cross. Many an undead war hero were aware of the benefits of running a relatively high defense and WS as a means to protect elite conversions. This forces enemies to counter march only with no trash offense to ambush.
So if we amplify the WS effect to kingdom level we force our enemies to squander the meter thus making the likelihood of one sided ops a possible consequence. In war we can use WS as a separator to achieve higher economy thus dragon funding, training etc. In zone tactics we can use WS to extend the zone and open on big attackers to prevent life saving ambushes when they're chained.
It's not a tactic used liberally unless you're outclassing your enemy by a decent margin. Dwarves will have built acres in 6 ticks and as campers makes them considerable threats. This tactic, if used with faery casting, can make the undead dark elf a viable alternative to traditional attackers. They will increase defense as war continues making multitaps less likely as war creeps along.