Well, falling damage only suggests, at the GM's discretion, that a fall from Extreme Range *could* warrant insta-death. Every other range would just mean a lot of damage and possibly a critical injury.
So that is a very, very rare case. It has to be setup at the exact height that they would insta-die and the GM would have to rule that they are, in fact, dead if they fall.
If the person has a bunch of critical injuries on them and the possibility of death is there then they definitely should know that before they make the jump, though GM warnings tend to affect player's decisions, so I try not to warn them in the moment.