Totally disagree. If someone is going to call him/herself a developer, he/she must at least know some backend programming and some frontend programming. Otherwise they're "being born" as incomplete developers.
At the company I work for, we've been hiring developers mainly based on a full stack job application. Most junior devs that apply to the position have strong knowledge on some area better than the other and that defines where they will be working, backend or frontend. Specialization comes afterwards you have experienced real world challenges and find what you're really strong at.
Unicorns (amazing real full stack developers that perform outstandingly well as frontend or backend devs) do exist, but they happen to be exceptional cases.