Unlike your average Kepler battlefield, in this one, different kinds and numbers of giant bugs will flood in with the advancement of time, indiscriminately attacking the human mechas, testing the pilots' ability to cope in complex environments while they increase in difficulty over time.
"Romero's choice of this kind of battlefield seems fair, but when faced with two super warriors, the constant emergence of giant bugs will increase the operational difficulty and load on the mecha. And as the advanced giant bugs appear, perhaps the Underworld fighter can cope - with bugs like those lurking, and mimicking, the Underworld comes with an anti-stealth system, but the Armor Dragon has nothing. That is to say, the more delayed it is, the more advantageous it is for the Underworld mecha. But I don't understand, why would Romero choose like this?"