Which FTOs guarantee jobs? I don't know of a single one that does so. Even the BA FPP and FlyBe schemes do not explicitly guarantee a job, although obviously the likelihood is very high. But that is with the scheme, not with the FTO.
I wouldn't trust published "employment" rates at all - it's just marketing ploy and anyone can reinterpret statistics in a favourable light. It's not the FTO that gets you the job, either; it's you. So you are the most important factor in whether you get a job.