This is not a mistake, it's actually intentional. You'll notice that the Titanium ones don't have any other special effect - enhanced flak is their effect.

Adamantian, comparatively, has crew killed on hit, while the Orichalcix ones have their Entropy effect.

Ahh, the repair modules probably fall in the same class because the titanium one is huge repair on a ship where the adamantium one is both ship and fleet.

I actaully like the different effects of the unique weapons, curiosities at work, often game changers hunting down those curiosities, you never know what ruin present awaits you.

The unique effects for different families of strategic weapons is great for adding flavour. I just think "being the best at flak" goes beyond interesting flavour; it is almost the only reason to use kinetic weapons. Furthermore I noticed it's not just the adamantium one, but also the 4th tier white kinetic weapon (basic unstable slugs) is worse at flak. So unless you choose the Orichalcix tech over Quadrinix in the final weapon tier, you're stuck with Titanium kinetics for the whole game for flak defense (unless you chose the Hyperium weapons).  :( I get what you're saying but it just feels more fun when the cool stuff you get from a new tech is actually better.