@geezer
As I have observed in other lineages, what they call
jam-sau is an action whereby the forearm is used to sink down on the opponent's arm as a block. Rather than the elbow coming in and forward, it is the distal end of the forearm that does the job. Often the wrist drops low (as in LT's SNT after
laan-sau) because the mind is more in the distal than proximal end of the forearm.
It has nothing to do with punching. Even when they have something they call
jam-sau, it is the idea of
jam elbow for punch training that is missing in other lineages. This means each stage of development that should be using this idea, instead has it replaced with techniques like
jat-sau, and on the opposite end,
taan-sau gets treated as a fighting technique as well. This is because the interaction between
taan and
jam elbows is missing! As a result, the entire system loses its coherence and becomes about techniques.