As the track hits the 2x4, the first bogie is lifted two inches. But the tank is not lifted nearly that much, because six bogie wheels are sharing the weight on that side. Therefore the tank feels a lift of more like two inches divided by six a very moderate amount. As the tank rolls on, the second, third and other bogies are lifted in turn. The disturbance to the tank is therefore minimal.
Governments can afford as many bogies, springs and shocks as they like.
To keep the two swingarms from assuming ridiculously different angles, various types of restraints, or couplers, have been used. Some are pretty basic analogous to the straps or chains used on some racing stock cars to keep their axles from dropping too far when unloaded during cornering. Crude but effective. The main reason for these modifications is to try to make one suspension handle both large heaves and small stutter-bumps a difficult task. For heavy impacts you need stiff spring and damping rates.