We already know Nintendo doesn't want to be associated with PM because it is copyright infringement, their policy also does not endorse reverse engineering their products due to piracy, it's also a game that involves IPs from third-parties. So not allowing PM on events they are partnered with is a no-brainer.
We also already know that Nintendo is a company that values control, being a family-friendly company they want to control everything related to their business, so having people who are actively representing them and are associated under a NDA contract in an event, or stream is also a no-brainer. If you have dealings with Nintendo, you won't be talking about PM or acknowledging its existence. So far, nothing we know has gotten us over that, what we already know and already knew for more than a year.
Do we know that Nintendo is hunting PM or just protecting themselves like they've been doing before? We don't have evidence strong enough to support such a change of stance. Nintendo has approached the tournaments clearly as a way to promote the newest Smash Bros. and the Wii U, so far I have no reasons to believe that they did so for another reason. That because marketing people at NoA are actually good at what they do despite decisions from japan and that's how marketing works, it's opportunistic by nature.
Reaching a conclusion that Nintendo is actively trying to make PM less popular for whatever reason when they have only publicly shown to not want association with it for obvious reasons is jumping to conclusions. And honestly, I'd not be surprised if twitch or any other common tournament sponsors jumped to those conclusions as well due to the sudden approach the did recently as we have no way to know if they were threatheaned in any way, it wouldn't be the first time noise has affected so many people due to the internet, and wouldn't be the last.
I can probably turn all this communication noise into a Masters thesis for myself, it's a very interesting case.