You can't build a space elevator without the required technologies. So the prerequisite technologies would get you access to the new toy. As for the high tensile materials, what other benefits do they have? Improved ablative armor? A more secure dome habitat for inhospitable planets. It's not like each tech need unlock a single benefit.
Precisely, the "High tensile materials" tech would unlock several of these, immediately, when you finish it.
I'd still point out that there are a lot of "theoretical technologies" currently on earth. For example, we currently have a working design for a warp drive, but it requires a material that doesn't exist (yet, or may never exist) and a power source far more efficient than any we currently have. A space elevator may be rendered possible by carbon nano-tubes; the only difficult being the expense of building one (and where to locate it. On a tall mountain near the equator is the best bet.)
Saying we have a working design for something, but that it requires a material that doesn't exist is exactly what I'm talking about. Sure, there should be some tech about "Spacetime Manipulation" that unlocks the Alcubierre Drive, but there is no justification, from a game design standpoint or from a "research works this way" standpoint. The things that would qualify as "Theoretical Technologies" are, in Victoria terms, Inventions, not "Technologies", and would be handled in the background via events if modeling to that level was important (My guess is the Devs feel no). When I direct my Physics science team to develop positron lasers or something, I figure I'm basically doing something akin to starting the Manhattan Project, not asking Miguel Alcubierre to sit in his office and postulate on some cool thing we could do with materials that we have no conception of how to make.
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