Yup, it's easy to forget that what we see is a tiny proportion of the footage available, and it's not the celeb who has the say in what is seen.
Talking of Zoe - no she wasn't defined by nerves but I well remember her "flu" last year which was harped on about for ages - I'm sorry, but if she was out of bed, it wasn't flu for pete's sake!
Just goes to show, different things annoy different people: and certainly the Beeb has a lot of control over how certain people are perceived by what they do and don't show from training VTs etc.
And once again, no it AIN'T strange that Emma could suffer from nerves: career has nothing to do with it. It's not something that every performer automatically gets "used to". A friend of mine happens to know an internationally acclaimed classical soloist, considered one of the very best in his field, who has been performing since he was a child, and he still gets nervous enough to bite his fingernails till he causes himself pain. If her saying she's nervous annoys you, then hey ho, that's a shame for her. But please, don't let's have this "she ought to be able to cope, she should not get nervous, it must be easy for her" - it's total rubbish.