I meant that we don’t support forward and deferred for the same platform simultaneously, which is mostly a code complexity issue (most shaders would have to be compiled twice).
Technically if you can change the value of r.ForwardShading per platform, you can do forward or deferred on each platform within the same project. There are some gotchas - when compiling shaders you have to look at the right platform’s setting. So this would not be hard to implement.
There are some challenges supporting both rendering paths within a single project though. The forward and deferred rendering paths are different enough that you have to create content knowing which renderer you will be on to some degree. For example, certain meshes will alias badly with MSAA, materials have fewer samplers available, certain rendering features don’t work in forward, masked materials work a bit different with AlphaToCoverage, etc.
In summary we still only support choosing the rendering path per project, but we might change that in the future. You bring up a good point for desktop games that want to have a VR version instead of being a VR game.