Context · Games
The Switch has some of the better parental controls in gaming and they live in a separate phone app rather than on the console, which is why most families never find them.
The controls are in an app, not the console
Nintendo puts time limits, age restrictions and a weekly report in a separate Parental Controls app you install on your own phone. It works well and it is invisible if nobody tells you it exists, which is the main reason it goes unused.
What the online part opens up
A paid online subscription enables play with people outside the house, and voice chat in most games runs through that same phone app rather than the console. So the chat your kid is having is often not coming out of the television at all, which is why it can be easy to miss.
The friend code question
Adding friends needs a code, which is a genuine improvement on open matchmaking, and codes get traded in school and in Discord servers. Worth asking who is actually on that list rather than assuming the code system settled it.