The
Saber,
Vanguard and
Katana are all essentially "battlecruisers," that is, ships with capital ship armament but which are faster than, not as well protected as, and not as expensive as true battleships. I've given them different designations to help distinguish them from each other, but they are somewhat descriptive. In the era before the war, the type of ship that filled the "battlecruiser " slot (bigger than a cruiser, but smaller than a battleship) was a hybrid cruiser/carrier that was used to lead squadrons of smaller vessels, and that would have been called a "command cruiser."
Saber was designed in this model, but because it was one of the first ships to mount the powerful new pulse cannon, it was produced in large numbers during the early part of the war as an alternative to building the more expensive, and comparatively outdated
Halberd battleships. The early pulse cannons were not as efficient as those produced ~20 years later, so four mounts was the most that a ship the size of the
Saber could handle at the time.
That is indeed an anachronism. I seem to recall having noticed it before and fixing it, but if so it somehow got un-fixed. I have re-fixed it.
That is a typo; it should read "medium blaster."