Quite. Perhaps a B777 pilot will also tell us what the HS would normally have been doing if the go-around had been conducted properly - with or without AP? Experience on other big twins with under-slung engines suggests that down-trimming is normally required to counteract the thrust increase AND the partial retraction of the flaps. So maybe the failure of the a/c to rotate to a go-around pitch when the PNF pulled hard enough to disconnect the AP was caused purely by the PF's unexplained pushing on the yoke.
The 777 FBW will auto trim the HS during any power or config changes so you don't feel the trim changes. Basically point to an attitude and hold it without feeling any increase in stick force. It's a SPD trim and only needs trimming in manual flight for any increase or decrease in SPD.
From the FCOM about autopilot disconnect force.
When an override force sufficient to move the control column, control wheel, or rudder pedals (LAND 2 of LAND 3 annunciated) is applied, the fly-by-wire flight control system will detect a difference between the cockpit controls and its own estimate of the expected positions, and will force a disconnect of the autopilot. After the autopilot is disconnected, the control system will transition the control surface commands from those of the autopilot to those of the flight crew
From what I understood the PF disconnected the A/T, applied full power whilst still going down the GS because the TOGA SWITCHES weren't pushed which would have put the aircraft in a 1500fpm climb. I'm not sure exactly how much force is necessary to disconnect the A/P but it could have been exaggerated by the increasing SPD.
The PF could have still hit the TOGA switches which would have forced the aircraft to climb as he had already applied full power although at a higher pitch angle. Alternatively he could have just used the A/P disconnect button on the control Yolk but like most people I suspect he thought the A/P was disconnected.