Considering the HUGE overall improvement i revealed in a WUST that some studios managed to reach from winter 2011/2012 builds to post-E3 ones, it's not surprising that Ancel went from "meh" to "wow" in this judgment of the system capabilities. We're talking of a 2X scale of increase, thanks to tons of parameters (new dev kit, a lot of new SDK, enhancements in middleware, engines, learning curve of developers, more and more familiar with the console specificities). Now, this improvement is surely not consistent across the board for every projects, but it's here, it's automatic, at least from the release of new dev kits and new sdk.
Really, the Wii U is a solid system, not a current gen one, if this precision was still needed.