So after reading a bunch of stuff on this it seems to me like Nintendo's aim here is quality control. There is a third party dock that's approved and out for the Switch 2 (and a version of it that's cheaper and literally the same product), and the Switch does a bunch of checks before it connects to test the hardware of whatever it's plugged into before drawing voltage.
Back when the Switch 1 released there was no such quality control, and third party docks got a reputation for frying your system if you used them because some of them would supply dirty voltage to the Switch when it was in its high power draw mode.
The device it's plugged into also needs a specific code from Nintendo to complete the software handshake, which is the big issue in my book. Nintendo could change the code at any time via a mandatory software update and break compatibility with your third party device, for example right before releasing their own version of whatever it is they will no longer be supporting.
Something else I considered while reading about this is that the stories of third party docks frying your Switch 1 might be Nintendo propaganda. Wouldn't surprise me but that's pure baseless speculation on my part. Either way I agree that what Nintendo should do is just conform to the USB spec, I'm just trying to read into their motivations a little bit.