To add to my post to Don above about updating games, those that don't play online and don't want to be banned will probably go to GameStop, buy a used game, update, and return.
The CDN is what gives you content and stuff. If you go to the eShop and buy/download a game normally, that's making a request to the CDN to make it give you content.
But there's the stuff the switch sends first so the CDN (or according to the reddit post @gameboy linked, something that comes before it) knows that "oh this thing is allowed to have content".
That's downloading from the CDN. That's fine!
But if we send the switch's stuff from another device, like our computer, and get the content that way, it's bad.
...yay writing smartass posts at 10:54 PM
So, downloading from the freeshop on 3ds will make Nintendo ban your switch (if the 3ds and the switch have the same Nintendo account)?
Nah, I really don't care if I get banned.