I am not sure if this addressed or not but YJM's Shaolin Long Fist has nothing to do with Northern Shaolin (aka Bak Sil Lum) they are different systems essentially.
I do believe there are many systems that can be lumped into the general term "Long Fist" and since I believe there is a saying that "all kung fu came from shaolin" I would safely assume most styles some how originated from Shaolin.
ULTIMATELY even within the Shaolin Temple there are many styles and systems.
So I guess in this case of YJM it's not the difference of players. interpretation, or lineage...they are simply not the same style.