ok, cool - my taiji teacher first put this to me several years ago, at the time it was not particularly PC, I guess - glad to see that this is now understood as such (not saying you recently came up with this, for all I know you figured this out ages ago, but it seems like a lot of peeps were not hip to this for some time)
in our style of taiji what most call Fan Through Back, we call Opening the Three Gates of the Back - Sam Tong Bei; my teacher always maintained that this also indicates the relationship of taiji to Tong Bei; actually, after that move, we do a 180 turn into a technique called Dang Yu - Waiting for Fish - that I have not seen in any other versions to date (but wouldn't be surprised if it existed in whatever proto-style it was derived from), and then we do Green / Young Dragon Exits Sea before moving into the next Lan Jaht Yee (Too Lazy Too Bind Robe as my teacher translates it); FYI, I study a non-familial branch of Yang Lu Chan; ostensibly our version of the form is a pre-Beijing version - we still have the jump kicks, the low spinning sweeps, etc.; another interesting thing - we also do our "jai" / press w/a semi-closed fist, similar to
here at 2:32)
awesome - thank you for your efforts towards "uncovering" the truth;