If they carry the votes over until next week, the overall scores will be very high, as each couple dances two dances in the semi-final. Not sure how that would work with the public vote. If the bottom couple scored 7s for each dance, that would be a total of 84 (28 x 3), and if the top couple scored all 10s (120), that would be a very large gap. Would that affect anything with the voting?? I need to ask my eldest son, who's a stats/maths guy.
Guess there's no way around it though. Deliberately creating a two-person final at this stage doesn't seem sensible.