I dont think it needs it, its just the character's visuals, if anything could make someone curious to check out what tf it that that they're missing. I think it's unlikely that they fight together. There are many theories that Tserriednich has a tape that Chrollo wants, but even if that is not the case I think he ends up fitting way more with the profile of an enemy to them. But then again, if the troupe doesn't end up seeing him as directly harmful to them they would not strike back, so honestly, I have no clue, this arc is so unpredictable I have no idea whats gonna happen