I had a similar thought but the author cleared it up somewhere on Tumblr I think. You can read below since it can be spoilers
Apparently V doesn't have schizophrenia at all and it was just the normal explanation the psychiatrists could give for their unnatural behaviour. And the nonchalance was a result of M's influence if I'm remembering it correctly? It's been a while since I read the explanation haha but I think the narrative will clear it up soon