certainly are trainable though, our friend/wifes Dom's german Shep is very good at knowing the time to and the time not to, Gail can be totally nude around his house and usually is, but if there are other "non-zoo" guys there he won't try anything, pays no attention to her, but if we are alone just me Gail and Doug (her Dom),, he will certainly shove his nose in her crotch or ass, If Doug says "No" he will stop, go lie down and behave perfectly, BUT, if he says "take her" or if she gets on all fours, he is in her!
then again he is 6 years old so the puppy is out of him and he has had quite a bit of experience