First up, let's break down with the Nintendo Creators Program is...
The Nintendo Creators Program is a service through which Nintendo gives you part of the advertising proceeds it receives from YouTube for your Nintendo-related YouTube videos. In the past, advertising proceeds that could be received for videos that included Nintendo-copyrighted content (such as gameplay videos) went to Nintendo, according to YouTube rules. Now, through this service, Nintendo will send you a share of these advertising proceeds for any YouTube videos or channels containing Nintendo-copyrighted content that you register.
Okay, now with that out of the way, let's take a look at Nintendo's updated terms of service following YouTube's overhaul of the Partner Program.
"Live streaming on YouTube falls outside the scope of the Nintendo Creators Program. You cannot broadcast content on YouTube Live from the account you have registered to the Nintendo Creators Program. If you plan to broadcast content on YouTube Live, you have a couple of options. First, you can broadcast content on YouTube Live from a channel that is not registered to the Nintendo Creators Program. Or, you can cancel your channel's registration to the Nintendo Creators Program and instead, register your videos containing Nintendo’s IP to the program separately. Videos which had previously been registered through your channel would need to be re-registered individually."
Long story short, live-streaming isn't allowed for YouTube accounts that are tied to the Nintendo Creators Program. It looks like it applies to people who have their entire channel under the Creators program. Obviously something that's not going to impact a ton of people, but those who are in this situation are sure to be quite angry. Thanks to Neomew for the heads up!