I'm just pointing out that there are indeed many people who buy Nintendo consoles only to play Nintendo games. The 3rd party support or the lack thereof doesn't matter to them because they won't buy 3rd party games on the Wii U even if they exist. To these people it doesn't matter if the Wii U is underpowered and misses out on multiplatform support as a result.
You can break this segment of the market up into two groups: 1) those who only play Nintendo games period, and 2) those who own multiple consoles, but only use their Nintendo console for the Nintendo games and their Xbox or Playstation for everything else.
But my overall point is you said it matters to him, but if he is in one of those two groups then it doesn't matter to him. No matter which group he's in, the Nintendo console is reserved solely for Nintendo games. Unless he doesn't fall into either of those groups, in which case you are right, but that's not true with everyone.