That's because it has to do with the specific person auditioning.
If Cachoo and I are talking about the same thing,
Spoiler
the favorite for the part came into the final casting call and, after auditioning, was asked to try to play the role more like she had at initial casting call months prior. However, she had gone through several personally defining situations in the intervening months and realized, to her horror, that she had not the slightest clue what she had done differently at the initial casting call. She didn't get the part. I don't know if this sounds at all interesting written out, but on screen, witnessing it, it was really very intriguing.