I think it's a bit of a reach to assume they haven't boned at this point, despite the fact they are flogging this relationship beyond credibility.
It's quite plausible that the sex is as flailing and mismatched as their dancing, thus the ironing board hugs and kisses and the failed piggyback. It's not a great sign that things are going smoothly but I wouldn't go so far as to declare it's all for show.
Maybe they're overjoyed that they've finally found their perfect shit sex match. That must be comforting.