It’s further towards the hard end of the scale, but not truly hard science fiction. Hyperspace is still a thing, and still plenty magical. Antimatter and even fusion power systems can provide really amazing amounts of energy, and direct control of gravity is just as magical as hyperspace, with a lot of implications the games don’t explore.
This is still absolutely a ‘science fantasy’ sort of story, but if you know some relativity and orbital mechanics, you’ll get more out of it. Ships don’t move the way they do in the games, that’s just unavoidable, but the shift to more realistic physics opens up all kinds of possibilities, especially if Applied Gravimetrics can make physics do things.
In Fallback Crisis, most of the civilizations in the galaxy can and often do throw things and people around their star systems at substantial fractions of lightspeed, and that’s just the beginning. When a fleet without a far jumper approaches a star, it has to stop to recharge every few light-hours, and any kind of competent defense system would spot them from light-days away. The artillery batteries around major planets are very much capable of throwing torpedoes at 15% of C, so approaching fleets have to deal with the defenders taking potshots at them with antimatter bombs.
It’s not easy for humans to understand the amounts of energy involved here, but the Tsar Bomb, the most powerful machine of any kind ever constructed by humans, is pretty small by the standards of space warfare. Hypervelocity projectiles are even stranger to a human frame of reference. If you double the velocity of something, you quadruble its kinetic energy.
When a defense battery hits a ship with a depleted uranium telephone pole moving at 3000 kilometers per second, it delivers 1,000,000 times as much energy as a regular mass driver that throws slugs at a ‘mere’ 3 kps. With the shots moving so fast, artillery can matter even if it’s as far away as the moon.
Far jumpers like Bentus and the Mothership can skip over the long-range battles, which is just one of the many advantages they possess. Even with more realistic physics, Homeworld would still be a story very much in the same vein as Star Wars, Battlestar Galactica, Kinights of Sidonia, and many others, and Fallback Crisis reflects that.