Unless you dont do WCK and dont know WCK.
Sergio brought up a great point in 3.23.
http://www.youtube.com/watch?v=I4eWIAYvf9Q
It is the signature of White Crane and Emei 12 zhuang's snake slide worm moves method.
Check out 4.46, emei 12 zhuang's little training set and see how it was done.
http://www.youtube.com/watch?v=uKASkDfmV9g
it is White Crane because the technic reference to center line.
it is Emei 12 zhuang because the way how the finger, arm and body handle.
clear and sharp in WCK.
As for why it is not HKM type of handling? The key is in the finger's last two joints handling.
Take a look and compare for yourself on the above Russell's 4.46 - 5.60 fingers joints handling and the following Lin's clip.
http://www.youtube.com/watch?v=HEe9CH3Y7Bg
From the clip, Lin's hand and finger handling while doing his set is closer to those who did Iron palm such as in Ngo Cho Kuen. It cant be the type which applied to finger specialist such as the WCK's Biu Jee. The handling is not fine enough.
Thus, the source of HKM cant be same type, it is a different type of art, with the WCK Biu Jee or SLT type.
also
Compare 0.35 of the following with 6.03-6.10 of Russell above on the finger wrapping to make a fist. (those finger wrapping are emei's signature called five fingers tracing taiji. this is what Jim Roselando talk about when he met with Emei's gate keeper)
http://www.youtube.com/watch?v=V5cqRp-YtuM
As for Sergio's question on Gm Ip Man's practice on BJ.
Let me share with you this classical case I happen to ask GM CHC decades ago.
As I was told by my Late sifu GM CHC on the way why GM Ip Man did what he did.
in Late GM CHC's word, " before one has the kung fu or while one is at training at home, one has to get every joints move to a large degree and cultivate the kung fu. after one has it, and refine it, one doesnt have to show it but all the minute move is in there. the advance the kung fu the less one will see the move of other joints. while in application, all those bigger motion doenst shown, you will only see the finger tip contact with slight wrist move."
That is how he taught me on the training and how he practiced it too.