I understand that it's wrong to compare the architectures, but this emulator being so well optimized can definitely run on the Wii U. The smartphone example was just to point out that less powerful hardware is still able to run the emulator.It's a different architecture altogether. You can't compare PPC and ARM/X86 clock per clock.
IPC is most likely very poor compared with a modern smartphone, remember the architecture dates back to 1997. Besides clock speed the biggest architectural improvement over Wii/GCN is out of order execution.
I think WiiU may be as fast as a midrange PC from ~2009.