No no he doesn’t need to call Nintendo you can unlink(now called de-register) your account from the Webpage, (https://en-americas-support.nintendo.com/app/answers/detail/a_id/22453/~/how-to-change-the-primary-console-for-your-nintendo-account) once a year
Also @Daniielx Bans are NOT ties to...
he could just unlink his banned one from the web page to not just the console -
>Using a web browser, visit accounts.nintendo.com. Sign in to the Nintendo Account you wish to deactivate. Select "Shop Menu." Select "Deregister Primary console”
(also re-linking the account doesn't get you banned...