I read somewhere on this website that WL is a soft rejection. Schools put so many candidates on WL ( like dozens for each category), the chance of coming off the WL is like 1.6%, even lower than the original acceptance rate.
So becoming FP increases one’s chances, maybe even double it, but it is like being increased from 8% (financial aid acceptance rate) to 16% (FP acceptance rate) for a very selective school.