[Precarious]

The thing about Charu claiming while being anything else is that it invites a counterclaim. That would be especially counterproductive for the serial killer, because the SK needs to survive four days. If the actual bodyguard counterclaimed or was lynched/transferkilled anytime in the first three days, it would blow up Charu's win condition. From a wolf perspective, I can't imagine how trading players would benefit them, particularly given that bodyguard isn't an investigative role.

Fakeclaiming as a VT is dangerous gambit precisely because it could draw out the real role for nothing. In this particular case, the real bodyguard (presuming it's a bodyguard and not an asceticizer) would still be immune to being targeted at night, but would risk the lynch on who gets targeted first.

The downside to his claim is that, assuming it's true and the wolves/SK take it seriously, there's no chance of them wasting a nightkill attempt on him. But having an all-but-confirmed townie that can't (or at least is unlikely to) be killed is a valuable resource, and one that becomes increasingly valuable as the game shrinks.