Thing is, you don't need canon or continuity to know when something is simply a mistake. When Ross (or Bennett or Whoever) said the Eugenics Wars was 200 years ago in DS9, my mind immediately knew it was an honest to god mistake. I don't need to come running down the alley foaming at the mount about how it violated some sacred document, I don't need it changed just because. It was a mistake. Spock said the Eugenics Wars happened in 1992-96, TOS has said it was two hundred years in the future so it exists at the tail end of the 22nd century, good enough. Two hundred years actually also comes up in "Tomorrow is Yesterday". They don't settle on the 23rd century until TMP advertising and novel, then in canon/continuity with TWoK. To me, none of it invalidates the 1992-96 date, two hundred years is rounded from roughly 250, just like Kirk and Khan both round roughly 18 years to 15 in TWoK.
None of it breaks the story or the illusion of the universe, and should be left how it is written until the franchise does a full blown reboot of the material.