While this document is likely true, we won't know for certain if these things are system-wide until we see them for another game.
Otherwise it could be just like Smash Bros. Brawl or Prime Trilogy, which had their own individual 'achievement' systems.
For the record, I hope if true of all Wii U games, they're optional. While I love the 360 to death, I don't like all the constant pressure to add to a cumulative score, or the constant reminders that X person got Y more points than me in Z game.