That one has to be one of the worse showings I have seen. This has nothing to do with Master Wong Nim Yi or any of the other true Wing Chun masters in China.
Here is a good one of different lineages of Wing Chun in China. I see Master Mak Yu Ming in the background.
If you want to see chi sao differently than the typical rolling check out Weng Chun. They will not always roll from tan to bong sao, but will stay in tan since there is no need to roll and turn you stance to bong if you partner is not pressing in. I different through process than ours (Ip Man Hong Kong lineages). I watched Sergio and Master Sunny So do this and Sunny was all over him every time he rolled to bong.
Here is a two man set with Sunny So and Master Tang Chueng Pak.
Good stuff.
Best....