And that's Role Morality, yup.I don't think that's accurate or fair. There are different working definitions of murderhobo, and they don't all necessarily include killing everything that breathes.
A (pragmatic) murderhobo doesn't kill the tavern keeper because there's no value in it. Pragmatic Murderhobos don't kill innocents (in part because of consequences, but also because there is no reward for it - it is thus inefficient). A temporary psychopath (perhaps a murdergodclown in training) might kill everyone they see, but that's different - they really do want to kill everybody.
But, okay, let's call what I'm talking about a MurderPragmatist.
A MurderPragmatist kills 'monsters' for profit, and for a MurderPragmatist the solution to most encounters with people and things that might loosely be called antagonists involves violence. Talk our way out? No, roll for initiative. Does the reason the group of elves is robbing caravans matter? No, not really, kill them and solve the problem. Talking might mean a long sidequest, and this is quicker.
That's "I've been paid to solve this problem." with a healthy dose of "I'm not being paid enough to think".
I would heartily disagree with the idea that that's particularly Pragmatist, however. Being pragmatic means thinking the situation through in a sensible and reasonable way based on what you know, rather than a whole bunch of theory. But talking it out is just as pragmatic as killing the elves. So is negotiating. Or running away.
Honestly, any of those would be MORE pragmatic since it doesn't involve you immediately risking your life except -maybe- running away if the elves move faster and/or are great archers.
Opening up with violence isn't sensible unless you've got a strong reason to believe that violence is the -only- way the situation can be resolved. Because then you're just cutting to the chase and not wasting time asking a bunch of useless questions and negotiating with someone who doesn't intend to actually avoid violence.
So, again, I would say your definition of a Murderhobo is just a person engaging in role morality. Where any moral compunctions they might have in relation to violence are set aside in favor of following orders. Though that -can- break down if the Elves start talking about their reasons during the fighting or before engaging the party. It's just unlikely to.