Actually it is the one part of the show I wish was done the DWTS way.
On SCD the bottom two are the bottom two, as far as the voting goes and I can see how this approach might encourage the couple that stays in to try and raise their game to avoid being in the bottom two again.
On DWTS though, the last two couples are the couple with the lowest vote and one other couple, but not necessarily the couple second bottom after the vote. This means from week to week all we ever know is who was voted off the show.
If during the show there has been any kind of disagreement or clash, then often the couple involved are left until there are only two couples. The idea is obviously to tease the audience about whether or not whatever happened might have got them voted off the show. It's a bit like being sent to stand outside the head's office and not knowing if you are going to be expelled or not!
So for example, this week we would have seen Anita & Brendan in the bottom two because they were at the bottom after the vote and the other couple in the last two, would probably have been Alex & James because James made it clear that he wasn't happy with Craig's comments and scores again.
I'd prefer this way of doing things because it is more exciting. I don't know if anyone else agrees?