I’m not going to check the whole archive, but going back to at least 2005, Nintendo was asking users to …
report ROM sites, emulators, Game Copiers, Counterfeit manufacturing, or other illegal activities
https://web.archive.org/web/20051124194318/http://www.nintendo.com/corp/faqs/legal.html
Here’s some more quotes from the same page where Nintendo is viciously anti-emulation:
The introduction of video game emulators represents the greatest threat to date to the intellectual property rights of video game developers. As is the case with any business or industry, when its products become available for free, the revenue stream supporting that industry is threatened. Such emulators have the potential to significantly damage a worldwide entertainment software industry which generates over $15 billion annually, and tens of thousands of jobs.
Distribution of a Nintendo emulator trades off of Nintendo’s goodwill and the millions of dollars invested in research & development and marketing by Nintendo and its licensees. Substantial damages are caused to Nintendo and its licensees. It is irrelevant whether or not someone profits from the distribution of an emulator. The emulator promotes the play of illegal ROMs , NOT authentic games. Thus, not only does it not lead to more sales, it has the opposite effect and purpose.
Personal Websites and/or Internet Content Providers sites That link to Nintendo ROMs, Nintendo emulators and/or illegal copying devices can be held liable for copyright and trademark violations, regardless of whether the illegal software and/or devices are on their site or whether they are linking to the sites where the illegal items are found.
Somebody has fed you or you have invented bad information. Neither Yuzu nor Ryujinx, the two Switch emulators which recently ceased development due to intervention from Nintendo, included Nintendo’s code. The Yuzu settlement required those developers to acknowledge that
There was never any mention of them stealing Nintendo code.
Ryujinx, we know even less about, because the agreement went down privately, but there’s literally zero indication of any stolen code. We know that Nintendo contacted the developer proposing that they cease offering Ryujinx and they did.
Obviously, Nintendo was bothered in both of these cases because the emulators do facilitate piracy, but that’s not the same as them having infringed on Nintendo’s copyright by using their code which you are claiming. Both of these emulators were developed open-source; if they were built using stolen Nintendo code there would be receipts all over the place. That was never the problem.