The title is from some flavourtext for the Irongrip Rails shoulder pieces, and to me it speaks massively to what separates the Banished from the Covenant. (Now I'm gonna ramble lmao)
Covenant were fierce, but known to stick to the same tactics and equipment nearly without fail, even when they stopped working. They were also focused moreso on adapting existing Forerunner tech, rather than innovating and creating new ones.
Elites will often show true disdain and hatred for human weapons, going so far as to call them "worthless even as trophies", or outright refusing to use the "heretical" systems. Prophets also heavily restricted the different species from knowledge that might advance them beyond their masters - keeping secrets like the inner workings of the ships they fly, how to reload their own weapons, and even keeping simple ore mining tech from the Jiralhanae, just so they couldn't rise up
Then along comes Atriox, not only equipping his forces with human weapons like shotguns, but using research on the weapons and tactics to improve his own. The House of Reckoning probably gave them an absolute tonne of tactical info too.
Now let's take the Mangler from Infinite - kinda feels like a combination of the Mauler and Spiker from earlier games right? I'd bet that's intentional - Atriox probably saw the predominantly Brute-only weapons, and their completely different usage and ammo types, and consolidated them into one single weapon that his whole force could wield.
As a mini closer, for a quick real-life comparison - after WW2, and with the formation of NATO, there was a push to standardize everything. At the time there must have been about 30 different rifle ammo types alone in use across Europe! Standardising on 7.62 NATO meant everyone could share ammo, and I think Atriox applied the same logic to his war machine.
