The system was introduced after last year's Olympics when America's Paul Hamm was awarded the all-round title after South Korea's Yang Tae-young was incorrectly docked a 10th of a point from his parallel bars routine.
After winning all their group games and helping to eliminate title-holders Brazil in the first round, newcomers Portugal came from 3-0 down to beat North Korea 5-3 in a dramatic quarter-final, thanks to four goals from Eusebio.
It will be the biggest all-British fight for a world heavyweight title since Lennox Lewis defended his WBC crown by stopping Frank Bruno in round seven of their 1993 contest in Cardiff.