Comment by _ph_

Yes and no. What they are currently doing, and it is working out greatly, is having a single hardware platform and a common code base on all devices. They still have branches of the main OS body for each device with the device specific customization. Which absolutely makes sense. Macs don't have touch. But iPads have. Which has at least some differentiation in the desktop UI. Then they try to keep up strong limitations on what iPad software can do - probably to a large extend to keep the lucrative app store alive. And of course, TV OS looks quite different for obvious reasons.