Alright, I guess I was wrong above; it certain is a "USB-C connector port." In fact, I would even say that it is a "USB port" (although they can't say that for licensing reasons.) Nintendo seem to expect and encourage you to plug USB-C peripherals into said port (e.g. any random USB game controller.) Nintendo will support such configurations just fine. You're not voiding your warranty by doing that.

What the port isn't, is a USB certified port. USB certification guarantees that it'll be safe to plug any USB-certified thing into any other USB-certified thing. Without that certification, the device isn't guaranteeing its ability to handle weird things that other USB devices might do—like sending it lots of current without doing a specific proprietary negotiation first.

It's a bit like FCC certification for "accepting radio interference." Devices that have it, are guaranteed to not melt down/throw sparks if you bring them close to e.g. HV power lines, or a radio tower. Devices that don't have it, aren't guaranteed to not do that. They might or they might not; but they weren't required to be tested to find out if they would.

But unlike FCC certification, where it's illegal to sell something in the US containing an antenna if it's not FCC certified, it's entirely legal to produce and market a device that has USB connectors, but isn't USB certified. There's nothing stopping companies from doing it—other than the expectation that consumers might care about the USB logo being on the product. If a company thinks consumers won't care about that in their case, they have no reason to bother.

(That's not to say Nintendo shouldn't have made their product fail safe under out-of-tolerance conditions from other USB devices anyway. It would just be good engineering to do that, even if you don't want to pay the licensing fee. But they didn't think to test for those conditions—likely because the USB Consortium wasn't invited to come breathe down their necks reminding them about things like that.)

I think there's very good justification for pulling USB-PD under the NRTLs and CE, so that non-compliant products are illegal to sell.

Compliance enforcement didn't matter much when USB was just data and low-wattage electricity, but USB-PD provides enough power to be hazardous. That risk is not currently being effectively managed.

"Buyer beware" isn't an adequate solution to avoiding device damage or cables catching fire.

That to me, is the key boundary being crossed, like enough to merit a large-class action award for any damages sustained anywhere by anyone who plugged a USB-C device into the port.

I do think there's something to be said for liability for creating a port that is so similar to USB-C, but also causing damage, akin to copyright laws, based on consumer confusion. I.e., if a reasonable person might think it is a variant of USB-C, and USB devices seem to work for long periods of time without apparent damage, then Nintendo is liable by virtue of resulting damage to the consumer's property (not to the USB organization). There's a certain liability for negligence in that case. But I could also see reasonable arguments that if Nintendo were explicitly saying it is not a USB port, that they shouldn't be liable (I don't agree but see it as a reasonable argument).

But if Nintendo is advertising it in anyway like that, they should be held liable. I just don't see a reasonable argument for why that wouldn't be the case. You can't have your cake and eat it too.

We don't really have class-actions in UK but under the Consumer Rights Act (CRA replaced the well known Sale of Goods Act) there's no time limit on when you can get manufacturing defects fixed so warranty repairs should be free (although you might also accept a brand new replacement and pay a little to cover the wear on your original).

In the EU there's an automatic 2 year replacement warranty on electronics too.

That seems like a bit of a grey area. I'm sure most people would assume that means it's a USB compatible port, but I'm also sure they would argue that they didn't explicitly state it to be a USB port, just a USB Type-C connector for use with the AC adapter or Switch dock.