Basically I think it boils down to the fact that, while it's possible for the Beeb to deny that a ringer has a particular advantage ('it was years ago they were at stage school', 'they only did a bit of dancing' etc), they can't deny that someone has been on the show and trained for x number of weeks.
I don’t think the BBC have ever made any justifications or denials regarding the extent of the previous dance experience of the contestants and their qualification for a place on the show, have they?
There’s never going to be any sort of a level playing field when you’ve got range of backgrounds from Olympic gymnast to retired politician. But the BBC aren’t remotely bothered about that because it’s not actually a dance competition per se, it’s light entertainment themed around dancing, hence the extortion to ‘vote for your favourite’ rather than ‘vote for the best dancer’.
If they were after a legitimately egalitarian dance contest they wouldn’t have had Debbie McGee and Brian Conley in the same cast. Because obviously Brian Conley was a stone-cold RINGAH!! 