Do you mean that in the real aircraft VNAV will engage automatically during a G/A
No, it's just that your video footage only shows a PFD, so I have to presume you pushed the VNAV button on the MCP when I see the FMA change from TOGA to VNAV.
But surely FLCH will give you THR REF too, or am I wrong?
FLCH will give an autothrottle mode of THR, THR REF, IDLE or HOLD as appropriate. In the case of a G/A it should set an appropriate thrust (approx 1.65EPR on RR RB211's) to achieve the level change in 2 minutes or 2000 ft per min. I would never expect the Thrust to drastically INCREASE at acceleration altitude as it appears to on your video. (It would give THR REF if you dialled in a large altitude change (say 45,000ft) in the ALT SEL window, only because the A/C then wants to achieve a rate of climb to get from your acceleration alt to 45,000ft in 2 mins)
I thought that V/S was a pitch mode. Do you mean that you should select V/S and leave the thrust mode in TOGA. How is this possible, won't the MCP automatically select SPD if you choose V/S?
Yes V/S is a pitch mode, but so is TOGA. I was alluding to the fact that in TOGA with an acceleration altitude programmed into the FMC the aircraft will reduce pitch and begin to accelerate (still remaining in TOGA). Some operators wait until this acceleration has begun and THEN select V/S.