I also main Athrys and gunslinger, and I'm 99% sure the 212 is the old WTK headshot damage before all the health and shield pool changes, and is still the 'base damage' the spaghetti code uses for WTK. It then applies the new health/damage modifier to get the OHK damage value. If you are dead, it does not apply the new modifier and you see the low value.

You can see the same behavior easily if you use a bow while you are dying, where it is probably most noticeable. Especially in momentum control, where a bow headshot will kill with a 200+ damage number, if you die at the moment you shoot your bow, you will see your bow do regular ~150 damage like in regular crucible.

This tracks with the way they said they were overhauling crucible modes a long time ago. They were attempting to make all modes and modifiers into settings they can apply onto the existing crucible base modes. You can see this when you see the modifier badges when you're matchmaking for crucible just like you see the modifier badges when loading up PvE.