It is not really any specific form it is applications of Chen Taiji rooting, Tuishou, Fajing and Chan Si Jin. You however gain understanding of rooting, fajing and Chan Si Jin form training forms and training Chan Si Jin and Tuishou is push hands. Basically he REALLY understands Chen style Taijiquan.
Chen Bing is very big on applications from what I understand and he started training with his uncle Chen Xiaowang at age 6 which means he has trained Chen about 31 years.
I have discovered there is a third clip too and if someone does not post it before I get home I will post it later.
Also from what I have read Chen Bing appears to have had no problems back at Chenjiagou with anyone who wanted to see how Chen would defend against just about anything that any student came up with and wanted to test him on.
Actually they ARE his students and/or fellow Tai Chi practitioners. That does not invalidate his skills but I can see how the environment the video was made in (a cage) could mislead a viewer. I believe that Xue Shengs last posted video has Tai Chi practitioner Rosario-Graycar getting thrown in the demo. Still nice stuff!