My understanding was that the thinking at the time was that the IP family protocols (ie tcp, udp, etc) would soon be replaced by OSI protocols and the sockets api was too tightly coupled with IP protocols and so your applications would need more difficult upgrades in the future if you wrote them against sockets. But your quotation disagrees with that claim. I think part of the implied benefit of the epic library is that it would seamlessly transition when the new OSI protocols were used.

Obviously, we now know that the OSI protocols didn’t get used (unless you count ldap or x509 or everyone talking about layers all the time) and so the more flexible api was not required.