The movement, and more importantly the body method behind it is expressed in Shiodas technique ...ala Daito ryu. In fact the rebounding is from an establishment of a current- the same as Mike's "ground path" (can't find a TM font) description and using that path as an internal spring. It is a training tool in DR. Which Ark knows about as well.
Whether it is Hiriki or chest matters not. So is the knee technique he uses. Its DR. and.......its in Tai chi.Gee what a surprise.
It also fits in with Hongs quote
"Without peng-jin, there is no taiji."
Sometimes I wish I were shorter though