It's kind of tough to tell what's actually going on here, because the relevant person here is a) not you and b) not inclined to talk in the first place. So let me just start talking and we'll see if something I say turns out useful.
Also you haven't said whether you're the GM here or just a fellow concerned player, so I will talk about "the GM" like they're not you.
Dungeon World, by default, assumes everyone is there.
Anybody can write bonds with anybody else. When somebody doesn't show up for a session, that means that anybody who has bonds with that character has some fancy-lookin' blank space on their character sheet. They can't roll +bond to help out somebody who isn't there, and they can't try to advance the bond during the session to mark XP for it at the end.
Now, maybe your GM has pursued alternatives to that; there are some of them out there like the flag system detailed here. Or my own personal hack, which is basically you decide who a bond is with when you roll to help, and at the end of session you either clear names out of your bonds or save the name to write a new bond around it next session.
But, by default, when somebody doesn't show up, everybody feels their absence, and it's worse the more characters are involved with them. I realize that schedules are what they are and adding guilt to the mix might end up being counterproductive, but I wanted to get that out there.
If people are feeling resentful that this guy is making their characters worse for caring about him, you might want to bring alternate mechanics to your GM's attention that won't do that, to stop the numbers from making things worse.
Dungeon World doesn't exactly let you not roleplay, if the GM wants to push it.
So, like, at some point the GM has pointed directly at this guy and said "what are you doing?" That's the kind of thing Dungeon World GMs do all the time.
"Hack and Slash", or any other move name, is not an answer to that question.
Hack and Slash is not something that you're doing. It's something that happens as a result of what you're doing, specifically attacking an enemy in melee. And, like, can you meaningfully attack that guy? Can you get into melee with them? Maybe you need to describe those things too.
Now, one of the skills a Dungeon World GM needs to develop, or a GM of any Apocalypse Engine game, is to specifically define what's going on, so that players can talk more specifically about what they're doing. "Fightgar, the chaotic melee swirls around you, what are you doing?" offers much less to build on than "Fightgar, Wizzrobe has blasted the goblins back from you. You've got room to go help Clericsdottir hold the line against that ogre, but the goblins are just going to regroup in the shadows unless someone finishes them off. What are you doing?"
But ultimately if a player just offers up a move name, the GM can just say "Cool. How?" until they're satisfied. It might be that this player has a pretty clear picture of what's going on, and all it's going to take is a couple more questions to make it clear it everybody else what's going on, too.
Then again, Dungeon World doesn't demand you roleplay, either.
If "roleplay" means "talk in character", I mean. Fightgar doesn't have to walk through his battlefield advance one muscle flex at a time, only say enough to establish how he's defying the danger of the rain of arrows. Stringfellow doesn't have to walk through his impassioned speech to the duke about the value of honor one word at a time either, only say enough to establish that the impression of the duke as an honorable man is sufficient leverage for Parley. The dice, in both cases, will take care of the rest.
Again, it may just be that the problem player in this case thinks he's said everything necessary, everyone else doesn't think he's trying, and a couple rounds of "How?" from the GM will help bring everyone's perceptions a little closer together.