A brief search on that wonderful 'Google' came up with this:
http://www.tracyskarate.com/History/his ... kenpo_.htm
I didn't read or cross reference this page. Like I said, it was just a very casual search, but maybe it'll do for an explanation of where things came from.
*edit* A couple other websites also say that James Wing Woo was the one that introduced many of the Chinese forms into the Kenpo Karate system, including the Tiger Crane set. Not sure how it was originally introduced, or whether it was introduced in a Hung Gar format but, after his time, was 'karatified' to become what it is now shown in the clip.
If you can't hit hard, hit them where they're soft.
Be charitable when listening to people, but always ask questions.