Not in my tests.
So I tested it some more and it appears I really can't make use of it if I don't have a domain registered with Sonic. Is this the correct assessment? While I can get my IP, I can also issue curl ifconfig.me and it will do the same thing. I can't associate a domain with my connection which will allow me to use list_api_keys so I can access my connection while I'm away from home which services from DynDNS and No-IP allows.
As an aside, is DynDNS a trademark of dyn.com? If you have no affiliation with dyn.com, you may want to consider using the generic term ddns.