Drakron, please stop making stuff up.
It was clearly stated that Revan had returned to the Republic commanding a huge armada of strange ships of alien design. I could agree with you if there were other ships composing Malak's fleet, but there weren't. In all the scenes displaying the Star Forge there's always a swarm of those ships around.
And the Republic ships shown in KotOR (Endar Spire/Harbinger model) are nothing like the Leviathan. Obviously, Carth's dialogue about the Leviathan and his serving aboard that ship are a screwup on Bio's part. Simple as that.
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Have to agree with 213374U, the Star Forge produced ship like the Leviathan, whch was clearly stated that they were of alien design.
The Republic ship were like the one that Darth Sion uses when he attacks you at Peragus.