It's trivial in the sense that it's low technical risk. I've not worked in the games for a while. At one company with an inhouse engine the rendering backend was initially DirectX9 written mostly by one person. He then implemented the Xbox360 backend. Another person did the backend for PS3 (OpenGL based). Don't have the exact timings it was ten years ago, but after the initial material, geometry lighting pipeline was done (and that's independent from the backend), the engine guy was never on the critical path.
They added Wii, DirectX10, iOS and Android backends while I was there. None of these were ever considered risky and none had more than one person working on it. Each console/platform has it's own quirks in how to optimise the scene for rendering but the having something rendering on screen is pretty much trivial once you have the machinery in place.
I can't speak for Epic, they are making an engine for every possible game and every possible rendering scene which is a harder problem than what we were doing. But the rendering backend isn't the hard part.
They added Wii, DirectX10, iOS and Android backends while I was there. None of these were ever considered risky and none had more than one person working on it. Each console/platform has it's own quirks in how to optimise the scene for rendering but the having something rendering on screen is pretty much trivial once you have the machinery in place.
I can't speak for Epic, they are making an engine for every possible game and every possible rendering scene which is a harder problem than what we were doing. But the rendering backend isn't the hard part.