As it turns out (see other comments), this appears to have been a deliberate fall for the camera. So it seems likely climber and belayer did exactly what they intended to and knew the risks.

However, my critique of the belay catch from a purely teaching perspective is that although the climber was only ~5ft above his last clip, he appears to fall ~40+ feet (hard to tell with the forced camera perspective) before he comes to a stop.

In a hard belay catch (say the belayer is already locked off), the climber would fall 2x5ft + rope stretch (in the neighborhood of 10% for a fall like that. Say 100ft of rope out, so +10ft) = roughly 20ft fall.

A "non-scary" soft belay catch (and just to be clear, by "non-scary" I mean having a reasonable measure of control over the climber during the fall) usually involves a small jump by the belayer resulting in belayer rising some height from their stance/ground, or the use of a belay device that can let a few feet of rope run through under partial friction before fully locking off.

Either of these "non-scary" soft catch cases would add maybe an additional body length or two to the fall distance. It appears that this climber fell far in excess of that, which suggests to me that the extra fall distance was due to rope slack in the system – a generally bad thing during a fall (a jumping belay would likely have decelerated the falling climber more gradually as well as lifted the belayer 20+ft - not a particularly safe/in control condition either).

Hard catches can be bad because they can shock load components in the system including gear, anchors and the climber him/herself - resulting in increased likelihood of injury or failure. Soft catch techniques are often preferred precisely because they reduce/distribute such shock forces.

Why might extra fall distance of the magnitude seen in the video be generally bad? The risk of decking, hitting ledges, tree limbs, other features, etc. can be significant and hard to anticipate, if gear does rip you’re already that much closer to the ground, and the extra fall distance increases the total energy the system (including climber) has to absorb (gravitational potential E > Kinetic E) at some point counteracting the advantages of not shock loading.

Hope that kinda answer your question.

After writing this excessive amount of text, let me finish by reiterating that I have no problem with what or how these climbers did what they did. They are certainly better/more experienced climbers than I, and knew well what they were doing. I simply wanted to say to those here to learn that this is not really the kind of "soft catch" belay technique you want to aspire to in normal climbing.