From the pix in this post, it seems to me that Cooper has a slight bump in the middle of his nose, where Bernstein’s is essentially perfectly straight. Which, ironically, reverses the stereotype of the hooked Jewish nose.
The prosthetic straightens out that bump, but in doing so enlarges the nose in a way that resembles Bernstein less than Cooper’s natural nose, IMHO.
I wonder if they were worried that people would object to Cooper’s natural bump as making him look stereotypically Jewish, and hoped to reduce such complaints with the prosthetic.