While Klingons like to speak of their "ancient" culture and Kahless and whatnot, it doesn't seem as if the Klingon culture of TOS or ENT would really be too similar to the Klingon culture of TNG. Probably customs and mores go in and out of fashion as leaders change, and/or as the fortunes of war change - and empty rhetoric about honor is spoken more loudly when the Empire is in a rut, suffering under a humiliating alliance with the do-good Feds. A triumphant Empire might not be uptight about honor, and might welcome Maltz with open arms if he has good intel on Genesis and the latest UFP torture techniques...
I like the sound of this.
I've always wondered if the 24th century era Klingons play up their cultural "traditions" a bit more for the sake of retaining something of their heritage. Not to say that Klingons really are all honor bound, but that they tend to exaggerate
those traditions for the benefit of everybody else. They're presenting the 24th century with a kind of 'Disneyland version' of Qo'noS, rather than the real deal.