Aren't bold dance moves just a proxy for confidence? If some guy is dancing flamboyantly, you can immediately assess the following:
1) Is this guy confident and assertive?(Yes)
2) Is this guy hot?
3) Does this guy know what he's doing or is he some awkward dork thrashing about?
With a guy doing some barely obvious rocking back and forth, you can really only assess #2. He could be a self-effacing milquetoast or a clueless schmuck. Which is a more efficient choice for targeted flirting, him or the Travolta wannabe?