I just thought these guys were a mix of Spock and Kirk's impressions of them and the computer records about them.
The computer records about Lincoln aren't going to be totally accurate. There's still a lot of speculation about him today. Whether he was really that much of a humanitarian etc. Surak seemed a bit of a jerk to me or was that just Spock thinking everyone hates him.
Maybe there's a thousand random facts about Kahless (some true, some not) in the computer and they've just chosen to use that one since the bad guys need some help at that stage.