It's easy to scoff at the timing, but as someone who's had laptops with Nvidia's optimus tech for the past 5-6 years, I can understand why. When you spin up the discrete GPU, even a weak mobile chipset, you can easily halve your battery life. If Apple hasn't quite perfected the decision around when to switch between the integrated and discrete GPUs, then that estimate won't seem very accurate to the average user. Watching youtube/netflix may or may not wake up the beefier GPU depending on how busy the machine is at the time, that sort of thing.

Personally, I'm starting to think that discrete GPUs are a bit overkill in laptops these days. More and more, I'm finding that modern integrated chipsets are up to the task of basic 3D modeling and graphical programming; the Linux Mesa drivers are even starting to support OpenGL 4.x and Vulkan.