Clearly you've seen an extended version because I've only seen
this and it's mentioned once before the interviewer moves onto discussing the sprint. Although I would like you to point me in the direction of that interview.
Unlike yourself, the cycling press need evidence before they can report 'cheating activities' because they can be sued for defamation of character which leads to settlement agreements and damages the integrity of the publisher. Hence it's reported as Ventoso says.. or Landis claims..
It's not unreasonable to ask for proof and to presume someone is innocent without evidence and the accusations by Movistar riders and a comment by Farrar isn't evidence.
My assumption would be that Farrar doesn't know exactly when they got back to the grupetto because it was fairly big and he was probably focusing on his own efforts only to notice Cavendish half way up.
I saw the photos at the time and if I remember correctly Cavendish wasn't in them yet everyone was angry about Cavendish cheating and not about anyone else. There's enough circumstantial evidence to convince me that he got help up Mt Etna but in this instance there is not.