I know this is going to sound weird and maybe a little bit late but it's something that everyone ignores.
If the Wii U is not powerful, then why would Nintendo showed tech demos to (according to Reggie) show off "what the system can do"
When was the last time Nintendo did that? not for the original Wii... it was the Gamecube and we all know that purple lunchbox was powerful and created some of the best graphics even today.
The bird and Zelda demos were gorgeous. People even thought were CGI and their jaw dropped when they learned they were interactive.
Also, they were done by early dev kits.
Nintendo had a reason as to why they needed to show those tech demos... don't you think?