That’s not actually true. The majority job of a GUI is text rendering. I recommend reading some of Raph Levien’s posts on the matter. It’s really hard to get quality GPU-accelerated text rendering. Games don’t have this requirement because they draw very little text and it’s stylistic so all the high-quality text rendering requirements are bypassed. Moreover they also probably remove the need for arbitrary Unicode whereas GUIs can frequently not make such a simplification. It’ll be interesting to see what performance gains are realized keeping in mind from a battery perspective the GPU may be sufficiently more power hungry that the efficiency gains are insufficient to make it more power efficient.