It's just a title but I do think it can be used to describe a very small percentage of people who are both talented designers and developers. Not just someone who can use Sketch and write HTML, but someone you could pretty much drop into any part of a product/app/website process and they'd be contributing at the highest level in the same way a more specialised "designer" or "React developer/whatever" would.

I always look at someone like Jon Gold as being a good example of design + code skill.