apparently using the assigned registration codes for the two physical machines I have doesn't actually accomplish this
Yes, registration codes were accepted that were used for SLED12 SP3. But a week later, can't get maint and I get some strange messages here is the first of several that are produced within a window titled "User Authentication":

URL: https://scc.suse.com/access/services...dule_15_x86_64

Check that this system is known to the registration server.
Authentication required for 'https://scc.suse.com/access/services/1561?cookies=0&credentials=Basesystem_Module_15_x8 6_64'

And so it puts our a user name of my email address and asks for a password. Nothing I have looked at with SCC matches this. And looking at the systems and how they are viewed, it seems that the registration codes were accepted.