Elevators have emergency breaks that activate if the cables and backup cables snap, so no elevators won't go into freefall if the cables snap, in fact elevators have so many safety mechanisms that they are ironically safer then taking the stairs
Mihari trying to assassinate onii-chan here. Stay upright, use your lower body to absorb the shock and protect your brain. Lying flat is a great way to guarantee you die. Broken legs heal, splattered brains don't.