That... is a very good point. For the inevitable modding, I wonder if we'll be able to individually set the eureka percent for each tech. With all the clamor for nerfs to 25%, it might make sense yet to leave these "cross-swim-lane" eurekas at 50% to fill the purpose you just described.
I find funny that the Wheel isn't needed except for military science. Planes don't need wheels, I guess. Railroads must run on magnets or something.
I am hopeful for civics tree modding to finally solve one of the gripes with cultural military developments and unique civ traits - the point brought up by Boris Gudenuf. If a good sizable number of civics were placed, which were dead-ends, and took commitment, and which enabled terrain- or socially- specific army technologies, it would , I think, be the best and first implementation of such technology. Civ traits could focus on things that apply in every era, and just one iconic UU, while the civics tree could allow everyone to match their strengths to their geographical situation and simulate the same necessity- or sociologically-stimulated military developments for which many civ simulationists have clamored for so long.
I'm very hopeful for this iteration. It sucks out of the box, but these bold core changes make a good canvas.