If there is nudity in a show or movie, will the producers/casting directors want to see the actors nude in casting? I guess to "see the merchandise", so to speak?
The answer will have to be "it depends". It's got to depend on the director, the casting director, possible changes to the script, etc.
An interesting case regarding script changes: One draft of the script for Close Encounters of the Third Kind included a topless scene with Teri Garr. However, that scene was never shot, and the actress never had to appear nude. She was not asked to appear topless during her audition (as far as I could discover).