There's a not-so-fine line being crossed here, between "Can we pretend that item X is part of a great continuum of facts, in which case we can further pretend that Starfleet did Y with Z? We can? Great!" and "See item X here? It indicates the author intent to have Starfleet do Y with Z!"...
Sure, the Oberth can be an old Vulcan design from 2178 or so. But there's no actual evidence for such an intent - there's just material we can pretend to be evidence for such an outcome.
Pretty much. It's just a theory that happens to fit the facts.