Yes, because how will you acces wireguard? Whats your endpoint?
I mean its all fine if you have a static IP which never changes but that usually is not the case anymore. So you need a domainname to update. Also vpn.youlab.tld is esier to remember than 131.234.142.83
Well ddns is just dns which get auto updated via helper script which you can do yourself on your own domain aswell. So yes Point still stands. And a domain which is yours might still be nicer than a bottom of the barrle subdomain. Of which you often also don't get unlimited