So, this glitch is basically an extension of the old focus taunt glitch. The reason that glitch works (I think) is because you can kara cancel the focus into any move with greater input priority. The problem is that almost nothing takes priority over a focus - if you try to do an ultra at the same time as a focus, the focus will come out. Taunting is the only move that most characters have access to.
Gen has something unique though. Stance changing seems to have more input priority than even taunts, so kara canceling a focus into a stance change works. Stance changing has very fast recovery, making it practical.
It's not quite as hard as it sounds. The difficult part is timing the focus to absorb the instant you hit the buttons; stance changing during the absorb animation is relatively easy when you time the first part right. It doesn't need to be on consecutive frames like a kara throw or anything.
Everything in the video was done without macros or shortcuts of any kind.
Edit: Wow, a Japanese player found this back in July.
Credit to the Japanese @wiki for the video itself and street11 for the link to the wiki. We're so far behind in technical knowledge. :(
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