Why now? Often the answer is, another tech's development enabled this one. Is that the case? They say here only:
> Vertical Walking is a new system to move yourself between floors in a building. By exploiting the potential of the human body and materials, only a fraction of effort is required, compared to taking stairs. No external energy is needed.
Maybe they use a capacitor? When going down, brakes store energy that supplements muscle power when going up? If that's the design, why not do it 20 or 40 years ago?
Perhaps it replaces stairs in constrained footprints, like dense urban housing, where stairs consume high proportions of space.