He is kinda right. Wii U fanbase is very small and they dont get anything than first party games. Why waste your gaming investment?
The decision couldn't possibly have been made recently enough for either part of that claim to be a convincing argument.
Also, if Wii U owners are only buying first-party games, it's because third parties are mostly screwing over Wii U owners with the versions they release. The few exceptions have seen the Wii U version selling well relative to the other platforms (like Rayman Legends, which is still selling best on the Wii U, despite the way that Ubisoft screwed owners over with their delay decision, or Sonic Racing Transformed, which sold about as well on Wii U as PS3, and not far behind 360, despite the much smaller install base).
ZombiU has sold to one in eight Wii U owners - not a bad result for a third-party game. Monster Hunter Tri for Wii U has sold a similar number, despite it being the third release of the game, after the Wii and 3DS versions (both of which sold over 2 million copies - making the Wii version the best-selling home console Monster Hunter of all time).
So when it comes down to it, a more accurate statement would be "Wii U fanbase don't buy inferior versions of games or late ports".
The funny thing is, when the PS3 version of No More Heroes struggled to sell compared with the Wii version, nobody said that it doesn't appeal to the PS3 audience, or that PS3 owners don't buy <insert whichever categorisation you want here>. Instead, it was brushed off as being due to the PS3 version releasing three years later. And rightly so - it was a late port, people with an interest in it already bought it for Wii. And yet, if a Wii U game that is a late port struggles relative to the original releases on other platforms, it's blamed on the Wii U audience, and not on the fact that it's a late port.
Hypocrisy is quite rampant within the gaming industry (and the gaming community, for that matter). Third parties will find any excuse to not release a quality product, especially on Nintendo systems. I always loved the old chestnut of "we can't compete with Nintendo on their systems, they're too good" - basically admitting that their games are actually crap, but spun as though it's a sensible business decision. Then there's the variations of "The audience for our games isn't there"... which is like complaining that there's nowhere in a field to build a house because there aren't any foundations already there - you're meant to lay the foundations yourself, and build the house from there (in this analogy, it's Nintendo's job to clear the land, but Nintendo can't lay foundations for third-parties' houses). I also found the "the install base isn't big enough" particularly absurd... it didn't stop them from ignoring the Wii, and didn't stop them from making games for the PS4 and XBO prior to launch, despite the former having the biggest install base of the generation and the latter having no install base at all.
And when they do release a relatively shoddy product on a Nintendo system, they tend to charge full price compared with the other versions. Mass Effect 3 was released practically simultaneously with Mass Effect Trilogy for the other systems, at pretty much the same price. Batman: Arkham Origins was released without the multiplayer, and everyone was shocked when it was actually $10 cheaper than the other versions - because all the other Wii U ports of games were being left with missing features but still having full price charged for them.
Maybe it's true that the Wii U audience doesn't care about Dark Souls. But that's probably because they have higher standards, and haven't been offered anything worthy within the genre. On the other hand, nearly a million PS3 owners were willing to buy *Haze*. You remember that game, right? Rated below 56% on Gamerankings, with the best rating amongst 66 ratings being 80%? With Eurogamer and IGN both giving it less than 50%?
So-called "hardcore gamers" like to say that Wii owners would buy any old crap, but personally, I've found that the standards on Wii and Wii U are actually higher, not lower. And when it comes down to it, third parties were right when they said Nintendo games were just too good, they couldn't compete. To return to the earlier house-building analogy, it's like Nintendo has built mansions in the area, and the little huts that third-parties want to build and try to sell for the same price as the mansions just aren't going to sell to anyone, because who wants to buy a hut instead of a mansion when they're the same price.
Note that I'm not saying the other systems don't have these "mansions". They do. This isn't about the systems, or the libraries, or anything like that. This is about attitudes within the various audiences - Nintendo owners have a higher expectation of quality, because Nintendo games come with a seal of quality. The seal looks like this: