No. Well, yes and no. If you look at it from the point of view of competitors, then yes, but if you look at it from the point of view of customers, then no - even if my favorite game doesn't get free bandwidth, because all that means is nothing has changed for me.
The problem with the net neutrality rules is they go too far. I agree with the concept in so far as service providers need to recognize who their customers are and not extort content providers - who are NOT the service provider's customers. The problem with the poster child (Comcast/Netflix) is that Netflix was never pushing content onto Comcast's networks - Comcast's customers, who were already paying for the bandwidth, were pulling it - that's how Comcast's customers were deciding to use the bandwidth they paid for. In addition, it was anti-competitive because Comcast offers it's own content streaming service.
What you've got here is a nice freebie T-Mobile throws in for it's customers, and it can't even do that without people complaining it violates net neutrality. Unless Nintendo is paying T-Mobile, I see no violation of the "ideal" of net neutrality, I see potential violation of the law because the law goes too far. Like the streaming services T-Mobile gives customers "for free" (it's not really, because they potentially suffer from reduced bandwidth for that content, but it's the customers choice - so be it), T-Mobile is NOT getting paid by the content providers for giving them necessary bandwidth - it is as it should be, the customers are using the bandwidth how they see fit - nobody is losing or missing out on anything.
The clash of ideas is the sound of freedom.