Don't confuse 'don't want to have' with 'wanting to not have'. Nintendo don't actively want 3rd parties on their console - they don't court them, they don't provide the services or tools that third parties want. From the early interest in Wii U from third parties, pretty much all of it has been dropped and Nintendo don't care. They aren't doing anything to get 3rd party support back. Ergo, they don't want it. If they get it, if they get license fees, great, but it's not something they are going to pursue.
That logic is exactly applicable to Wii and Wii U, but Nintendo still released under-powered machines. Why didn't they put more power into Wii and Wii U so people wanting to play COD and Madden et al in HD (160 million ish going by PS360 numbers) could get a Nintendo console? Nintendo have low-balled everyone's expectations twice in the console space, and similarly in the handheld space although that is at least justified by battery-life. Low power hardware is Nintendo's modus operandi. A belief they'll put in reasonable specs in their next machine is a view that contradicts existing patterns, plus one that contradicts the sentiment of having a hardware platform that's supported in mobile too. Plus you're talking about 16-14nm parts where Nintendo can't be sure they'll be available. Designing a system now, they have to factor in it might be at 20nm when released. Sony were bitten by that with 65nm and it cost them dearly. Given Nintendo's cautious nature, it seems unlikely they'll gamble on a latest-greatest lithography and squeeze in more power. Instead, they'll choose moderate power at 20 nm and process shrink to get lower production costs and more profit margins if they continue their current patterns of behaviour.