Skyline
As I've highlighted, FFC isn't talking about the ref but an 'extra official' (presumably someone like the video umpire they have in top-class cricket).
Personally, though, I agree with you and DG - it has to be some system where the ref is given an 'instant' (or realistically sub-0.5 secs) notification - say by a buzzer on his belt - that a goal has been scored.
Thanks, I had indeed misread that.
Still don't like the concept. The ball is either in the goal or not. To make it an arbitrary 5 seconds to decide when anything could happen in that time and we've seen enough instances where the video evidence is not necessarily straight forward makes me anti. And when there is a better, simpler, more immediate, already trialled option i can't see why you wouldn't go with it !