No, GANs train exactly one discriminator, jointly with the generator. There's no guarantee that you can't train another good discriminator out of band.
Furthermore, GAN discriminators are (as I understand it) often hobbled a bit to ensure that the generator can make progress on the loss function. An always-correct D doesn't provide a useful gradient.
Furthermore, GAN discriminators are (as I understand it) often hobbled a bit to ensure that the generator can make progress on the loss function. An always-correct D doesn't provide a useful gradient.