i'm--pretty sure that'd be grounds for a lawsuit. if the offended player would be so inclined to pursue such a thing. would be an amusing use of downtime.
i don't actually think you'd get flanking even if you landed in a flanking position, since the check is made during the jump, and either way the check is initially to JUMP, not to attack the target. i don't think it'd be unreasonable for a narrator to give the flanking bonus, but RAW i don't...
something to note: one of humanity's specialties is throwing things. other primates can kind of throw like humans do, and there are animals that have their own ways of "throwing", but humans throw the fastest and most accurately by far. from what i can find this is mainly due to how our thumbs...