No, hitting an lc bc osf in a pw, so plunder should have gone up if the plunder cap increased. Bought more allies and nothing changed at all. I had the same discussion with a few ppl convinced that the plunder cap should go up, till some1 had me test it on their alt before converting a Guild into an SoS. (Their alt was lc bc SoS osf). Plunder dropped. My guess, emphasis on guess, is that because the gold made from steals has gone up significantly the Dev's have made them more 'separate' from troop buildings by making them less of a benefit to troop buildings, and instead earning gold through actual steals. Also in their other game FC, they have made a change so that plunder bonus drops with troop loss so Hansel's with high ally stats can't war from DTW positions and still make a lot of gold. They can't do that here because ppl have spent months building kingdoms around strategy's, you can't just change the game mechanics. So I'm guessing they have changed the building's in the tier 4 rollout to prevent that from happening without changing game mechanics. Try it yourself. Build a Guild, hit an lc bc osf, switch to SoS and try again, plunder drops.
But don't get me wrong, I'm in no way complaining or anything, this is an awesome guide. I look up building stats on here a few times a week, and I had the same view as you until 2 weeks ago when it was proven to me.