The funds were likely sent out before Multi-Sig was so widely used. I think all of the treasures are legit and all, but they are definitely not immortal!
It probably wouldn't have made sense to use multisig when the funds were originally distributed (or more likely it wasn't even a thing then) but now that we have the technology it makes a lot more sense to use it. It seems that most of the treasures are legitimate, but don't forget about the CIYAM incident.. Although everything ended up alright, multisig would have prevented that incident.