DNS and NetBIOS are not the same thing. To fix DNS, the migration procedure runs this script, found from the implementation link above: ns8-samba/imageroot/actions/import-module/80set_nbalias at 6364825ded9905f94910994f8f674deeee366b4c · NethServer/ns8-samba · GitHub
It actually defines a CNAME record for the netbios alias. I suggest to define an alias and not rename completely the DC with netbios name
because you’d get unpredictable side effects in AD configuration.
You can also change DNS configuration with MS Windows RSAT tools.