It won't be difficult to change the names, just as they changed the insane name to erratic. For them to argue that we already have roommates, when people have explained what they mean by having an NPC living alongside you, is just needlessly pedantic and to be fair, kind of arrogant. As MadamLee pointed out, they're not gaining any income from the NPC so they're not renters.
Plus the label "roommate" serves no purpose outside of CAS, it's really just a way to say when making Sims that they're not related. If they're really opposed to something so simple, they could just call them housemates instead.