My thoughts..
He used Assassin's Creed as an example... First of all, think about a Ubisoft game that WOULDN'T work on-the-go as it would at home on a TV. We already know 1 confirmed game that Ubisoft is developing for the NX where this would be the case.
Just Dance.
You wouldnt be able to play JD on-the-go the same way you would at home. Ubisoft would have to change the game up for this very reason.
A game like Assassin's Creed, they wouldn't have to do this unless the dock DOES add more power which is likely not the case for launch.
At least some people are thinking the same thing I have.
http://m.neogaf.com/showpost.php?p=219131321
It feels like it's to play with different control schemes, not to have different power envelopes. Otherwise we are back to square one with the dock but there's been no rumours that the dock has a GPU so again. Most likely the NX still has one power state or the possible upscale or uprender when docked.