I think the fact there is both mafias and serial killers, may be giving people more reason to be quiet than in a game with just mafias. At least that is how I tend to think about it when I am playing on town of salem - because there are more kills, talking a lot, being helpful, or being controversial will probably get you killed in the night (well, or hanged, but that is often very silly).
But I think that the bad roles have even more reason to be quiet, because if they are killed or targeted by certain town roles they are very likely to lose. Town do not necessarily want to get targeted, but it is more important for them to try to figure things out during the day.
Partly because of this I am most wary of roundbox at this point. I cannot tell if he is legitimately as bored by this game as he is saying, but I see more reason for a mafia to claim to be and kind of sneak under the radar that way, than a town. I also think it is less normal for him to not end up voting anybody, which again I think is a better strategy for mafia not wanting to be controversial than for town. If he could speak more to why he did not want to vote ffa despite finding his play weird, and why he did not want the kitb, that might help. I see
this as trying to convince other people to move to Cel instead of ffa to avoid the kitb, without going out and saying it.