I think porn as it is, was formulated around the 70's. before that it was quite different, focusing more on funny stories or jokes. 20's porn looks more like laurel&hardy than the deep throat. martial arts genre is a couple of decades older I think. maybe there really is a connection between the bruce lee craze in the west and genre-movies? sounds possible, even likely.
maybe the influence went from early westerns to pre-fifties east, came back as kung-fu flicks, and contributed to the 70's porn genre?