I was so intrigued by this that I got that "Transcribe" application and tried to figure it out using that. If you can imagine the timing of the first four plucked notes on strings 5-4-3-1 then believe it or not he is keeping the "usual" plucked timing but is somehow shoving in two more plucked notes between the 1st and 2nd notes of the "ordinary" pattern. These are the plucked 3rd and 4th strings. It's some kind of 2-note chord light-speed sweep back!
I can hear it clearly in the slowed down playback but am at a loss to understand how anyone could pluck that fast.