@Hitman928 That's not SoC power, but GPU power.
You do have a point about it being peak power.
Nevertheless, you can see a true 15W system uses ~30W(plus or minus 10%). The Slim 7 cannot be a 15W device.
There's also no point of a battery life test on a reference system. I remember when they used to do this. The Sandy Bridge 45W system with the iGPU had great battery life.
In reality, barely anyone used the iGPU-only setup and the battery would huff and puff to get 2.5 hours, which is less than half of the 6 hours the reference system got. Actually the U systems rarely reached 6 hours.