If we're talking about conventional engineering, then knowing that something is possible can limit search spaces, which increases the potential for proliferation of a piece of technology without the total sharing or transfer of its design in complete detail. This usually occurs when a piece of technology is reverse engineered. For that to be feasible, you generally need to posses some elements of the design in concrete form. Even only photographs of an aircraft could qualify, but the more data the better, such as knowledge of what types of materials are in the supply chain. There's nothing metaphysical exhibited in this process.
