Of the 8 energies of taijiquan: I can find nothing in the video.
The striking object does not reflect or move power the right way, it is soft in the wrong way and hard in the wrong way. You want sometime that moves softly, but is hard, not something that moves hardly and is soft!!!
His skill will go up at first from this type of training, because he will gain percussion and precision from this. He is not issuing power into the pad, but is instead using percussive force, which rebounds back into his body, damaging his body and skill in the long run.
This type of training is common for Karate, but is not traditional for Taijiquan. The Japanese styles are as notorious for destroying the body over time as the Japanese are proud of bearing pain without complaint, the masters don't speak often of the damage their training because to them to be honest about injury is a weakness.
Training in taiji follows Tao:
http://ariyavansa.org/dc-home/dc-009/
Stretch (a bow) to the very full,
And you will wish you had stopped in time.
Temper a (sword-edge) to its very sharpest,
And the edge will not last long.
When gold and jade fill your hall,
You will not be able to keep them safe.
To be proud with wealth and honor
Is to sow seeds of one’s own downfall.
Retire when your work is done,
Such is Heaven’s way.
His skill is good, but it simply is not taijiquan.
If you want a simple explaination:
He is trying too hard.