Or he says:
1) Technically not possible on the engine (though I don't think he meant that and BF2 could reload while in sight mode?).
2) Working the bolt while sighted will have a slight effect on your aim, yiu won't remain 100% "laser" accurate, while moving the bolt you might move the tip of your barrel a little bit away from the target. Or in short: You probably won't be aiming exactly where you did before (though close to it).
3) POint 2 might not really work out in FH2/BF2, a small temporary decrease in accuracy or knocking your aim of a little bit while sigted doesn't work. So we could only add this if it would mean that your aim would remain laser accurate (dead on) of your previous aiming point (pixel). Or simply said: It would be too easy to exploit ingame.
Just guessing, as your video showed it is possible to remain sighted and work the bolt. Hahaha (should we be running away now?
). *insert distraction here* *blinks* *laughs* *silence*