After some more tinkering, I'm pretty sure it's there to prevent over-articulating of the front half of the chassis, preventing damage to the drive shaft and coupling between the two independent driven sections.
In other words, if someone tried to run it through a curve less than O72, it would bottom out against to inner wall of the boiler and force a derailment before the truck turned far enough to bust the coupling and shaft.
So it does have a real purpose and is not just for show. Guess I have to modify my smoke mount.
