LOAF: "The following information is a compilation of facts offered by Ralgha nar Hhallas and gathered by Terran Intelligence and various Covert Ops."
Yes, I know that Hobbes could be telling them bull (and himself believing in it). But, as you can see, Intel and Covert Ops also took part in the information gathering. Furthermore, note that the last revision date is 2668.312. Now, wartime or not, I am 100% sure that some crazy Confed anthropologists (like Zero's father) would have by this time gone over to visit Ghorah Khar and the other three Kilrathi-Confed planets. Furthermore,
"The Kilrathi writing system was first seen in the cockpit of a captured Dralthi fighter".
That should conclusively prove that the information is correct.
As for the other sources: The WC Movie can be immediately discounted. Yes, I know it is canon, but nonetheless the differences in visuals are too huge. The language shown in the movie was the language of the Movie Kilrathi. The KSaga language is the language of the Game Kilrathi, circa WC3.
The other source is WCP, and that's the only place where I have seen that particular type of writing. Now, vertical lines wouldn't have looked very cool in that intro, would they
?