I've worked with lots of designers before (I used to be the only programmer prototyper in a design studio serving a bunch of product teams). I never had trouble communicating with designers. In fact, they were much clearer in communicating designs than any SE-background project manager could ever describe in a spec.

The product teams, however, would often come back and say "this is too hard", and my job was to code something up in a few hours and say "no its not".

Whether it is a coder that knows how to speak design or a designer that knows how to speak code, that translator role is absolutely crucial. Without you there to bridge the gap, product creation might have ground to a stop.

I definitely wasn't versed in design before I joined; what made me useful is that I was working "with them" rather than working at an arm's length in another team. Usually, it's the PM's job to coordinate, but design-skilled PMS are rare.

Designers embedded in engineering teams can also work out, but lose the peering benefits of working with other designers in a studio setting.