Without the long action, the COL would have been limited to 2.800". The tends to raise pressures a bit with bullets heavier than 165/168 grains. The 180 grain bullets intrude into the case some when seated to 2.8", effectively reducing the case capacity.
As I stated before, action length has nothing at all to do with cartridge overall length. What does affect overall length is the distance from the bolt face to the lands. The chamber on a short action can be equal in size, or bigger, than on a long action.
In short, I still dont buy your story.