This isn't holding back or deliberately not using the most familiar weapons; rather, it's about strategically choosing the right gear.
Because the opponent Kalduce isn't wearing Terminator Armor, just a set of regular Tactical Powered Armor—although the model is a bit rare, the 'Majestic' Powered Armor is something many Battle Groups would be envious of.
Using a Thunder God Hammer, which is more than enough to take down heavy units, against an opponent in Regular Powered Armor isn't suitable. Something more flexible like a Powered Sword would be much more appropriate.
To be honest, the gear Cao Boyang is wearing is far more expensive than what Kalduce has on. If this were a war, Cao Boyang, in such attire, could play a much stronger role than Kalduce by many folds. Suppressing firepower, charging into the fray... he could do it all.
But a duel is another matter.
