You are right in most of what you say, but see, I find it good to say "I am a back-end developer" because I don't want to / I am not interested / I am bad at front-end technologies or user experience.
It allow us to try to fit there were we are more comfortable. How would you express to "outsiders" (like a recruiter) that "you don't feel comfortable with front-end technologies as you do with back-end ones"?
The "I am a java developer" point of view is sad and I agree with you. If you know how to develop, you will do that in any language, maybe faster or slower depending on how much you master the language, but you will do it.
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