Either way, Black Siren's plan probably isn't ideal for what Fallout wants, but it's hard to argue that Team Flash has his best interests in mind either. After all, Fallout is finally back in Central City after being stranded on the vacant Earth-15 for quite a while, and it probably wasn't very much fun being stranded alone on an empty planet. Plus, Fallout is one of the last remaining metas that The Thinker has yet to obtain, so obviously, a plan that gets him out of the city might be better than whatever Barry and the crew has planned for him. After watching Team Flash unsuccessfully protect every meta he's gone after thus far, can anyone really blame Fallout for taking his chances with someone else?