You can see the email that the user is claiming came from AMD’s Customer Care department. He sent an email asking whether the rumored speculation of the Wii U’s GPU being based off of the AMD Radeon E6760 was true. The E6760 fit all of the descriptions of what Nintendo says is in their machine being 40nm.
In addition to that the E6760 consumes a low amount of electricity and is one of the first GPGPU’s out there. It fits all of the descriptions of the Wii U’s GPU.
The AMD rep notes that while the Wii U uses a E6760 GPU that it is customized which means we should remember that the specs of it running inside the Wii U could differ wildly from the specs of the GPU off the shelf.