That’s 90DNS. It black holes Nintendo Servers at the remote DNS level. There’s an ongoing debate as to whether or not DNS resolution coming from other locations (such as 90DNS) has an impact on your download speeds. I say let the facts speak for themselves and test if your downloads with and without are significantly different for YOU. If YOU can’t tell the difference then they are the same. Nobody else matters.
The risk for 90DNS IMO is that it has to be set up on each network you attach to before you start sending data on that network. Go to a friends house? Plug into your Dock? Change wifi routers at the house? All opportunities to forget to set up 90DNS.
Other than that…I love it and use it myself. It’s all about layers.
That said, I also run this:
https://rentry.org/ExosphereDNSMITM
It’s built in to Atmosphere and makes it so DNS queries about Ninty never make it out of your Switch. They are instantly resolved as 127.0.0.1 (basically your own internal IP…so it kills them because your switch won’t respond like a Ninty server does.) It also comes with a Prodinfo “blanker” which removes your Switch’s identity so not only can you not lookup the DNS, even if you did, Ninty would block you because you don’t have a valid Prodinfo value.
On top of that yiu could take it one step further with Incognito_RCM and actually remove your Prodinfo (vs masking it) from your Switch completely. The only downside is if you don’t keep a backup so you can put it back you are technically permanently banning yourself. Good times.
Bottom Line: At least do this right away
https://rentry.org/ExosphereDNSMITM and think about doing 90DNS and Incognito_RCM at your leisure.