I think he meant sneaky, or something similar.  Snarky more accurately describes himself.

I really like it being optional.

Man, look at the 4Gb x360. Some physical games simply dont run without an HDD, the HDD was mandatory for playing it.
They wisely skept this by making optional the files instalation.
You dont need an adictional HDD to play, you just need if you want a better performance game.

Have it ever happened in consoles before?

I had a few PSP games with optional installs (Hot Shots Tennis, Peacewalker), a few PS3 games (Valkyria Chronicles, some other...I'm drawing a blank!), and Xbox 360 (Dragon's Dogma DA) that boosted performance quite noticeably if you install the optional bits.

There are multiple other games on other systems that allows optional install (KHBBS for example)

Pretty interesting! I don't mind the add-on data. How many games have we seen anyway with "improved gameplay" as patches?

They could not fit it on the physical disc. The game takes up 23GB and they opted not to go 2 discs

planning on downloading the game, so I assume none of this applies to me.

Wonder how long it will take to download, with our pathetic 5 Mb/s.

Not if you don't value your time.

Interesting; to my knowledge, this is the first Wii U game to use this method.
It was common on PS3/360 to try to alleviate RAM and disc drive streaming limitations.