These modern double-clutch gearboxes were originally developed for motorsports applications. In a racing car, the objective is to maximize the performance of the tires by expending the traction budget to the greatest extent possible. Minimal shifting intervals (on the order of of ~60ms) are required.
The duty cycle in an armored vehicle is very different, obviously, and shift times of 1000 ms are prefectly acceptable, and in fact, more comfortable in such a large vehicle. Given that modern torque-converter automatic transmissions are exceptionally reliable, there really isn't much incentive to adapt a new technology when the existing solution is both well-understood and quite durable in service.