Well...thing is, the quote states "The first recorded contact with the Kilrathi was made on 2638.229, when the exploratory vessel CS Iason encountered three armed Kilrathi merchantmen"...which doesn't really mesh well...
Let’s not give in so easily to a seeming conflict. I think in this case we’re making a mistake to read the words “recorded” and “contact” so broadly. Keep in mind that Taggart had physical contact with the Kilrathi as a result of this incident and that he subsequently escaped to provide Confed with a firsthand account.
Also, for what it’s worth, some of the references to prior “contacts” with the Kilrathi, such as the history of the first Iason encounter (in
CM,
VoW, and
VS) and early Confed intelligence reports on the Kilrathi (quoted in
AS) are notable for the apparent poor quality or vagueness of the “record” or information on which they’re based (especially the inability at the time to even identify observed ships as Kilrathi).
Finally, the quoted passage from
TCH is “in-universe” and more to the point is from a
HarperCollins Student Encyclopedia dated 2653. It’s only what the
general public claims to know, which still leaves open the distinct probability that the public has not yet been told or learned everything there is to know about other “contacts” (not to mention the details of Taggart’s own experience). As for Dr. C. L. Kohl’s “encounter” in 2621, the only “record” we know about is his “notes” of his
secret observations of the Sivar-Eshrad ceremony. I don’t think we know what the source is for his reported capture and execution (and I’m not sure we otherwise know how or when his “notes” first came into Confed hands, let alone how or when they were first disseminated).