That's the expectation in America surely, but is it in the UK? In America people are told to get the fuck out of buildings as fast as they can when the fire alarm goes off, but in the UK people are told to stay inside high rise buildings, apparently because they have fewer and narrower staircases. Highrise buildings in the UK are evidently not designed to be escapable. I think that should be the real scandal. The cladding is bad and effects hundreds of buildings, but how many UK highrise buildings have inadaquate stairways? Tens of thousands? More? The reason this isn't part of the scandal is probably because the scope of the problem is too enormous.
I encourage you to look up the timeline of events inside Grenfell; if evacuation began when the fire was called in, there would have been ample time for complete evacuation. 14 minutes elapsed between the initial call and fire spreading out the window of the origin flat. People were only reported trapped by smoke ~40 minutes after the fire was called in. These people were killed by the UK's policy of staying put inside buildings on fire.
Anyway, I've seen some videos of people falling a fraction of 15 meters onto pavement and dying. It seems depraved to expect somebody even on the third floor to jump onto pavement.