Oh, that is sick! I was gonna ask if any were in Nitrobe77. Would be awesome to see more of this stuff in production knives (or customs for that matter). Though, much like Vanax or other high nitrogen pm steels, the raw material cost is quite high. I understand heat treating can be tricky, as well, since it requires the right partial pressure to prevent unwanted de-nitriding or even unwanted additional nitriding of the steel.
I don't think the Anax was intentionally designed as a front flipper. At least, when they first came out, I don't remember them being advertised as such.
I think you're right that they're not more popular in the US because we've become so accustomed to Kit-Carson-esque or "back" flippers. As with anything, it does take a little practice to get used to. It's the same with certain flipper designs and flipper placement on other knives, though. However, now with the advent of bearings, ceramic detents, adjustable detents, etc., makers have the resources to really execute either back or front flipper designs well for all users.
I personally don't think the execution or design would be all that much more intensive. Honestly, looking at my large Sebenza, I think Chris Reeve could easily modify the design into a front flipper. In the closed position, the blade spine already juts past the front of the handle. Would just need to extend that, move the stop pin back about half a centimeter, make the choil cut more vertical and forward about the same half centimeter, and voila! Front Flipping Sebenza! Also, since the front flipper design is popular with South African makers, I think it's a little strange CRK, who started out in South Africa, didn't come out with a front flipper version of the Sebenza.
The way that Chad Nell (Trico, Utah FF) and Enrique Pena (Zulu, Apache, Trapper, Barlow) do their front flipper design is pretty much spot on, IMO. They have the flipper tab in more of a "top flipper" position and the tab is so unobtrusive as it follows the contour of the front of the handle and feels natural to engage (I use the distal digital crease of my thumb to grab the jimping on the flipper and rotate the knife out).
Reate's Bushido and Tribute is pretty good, as well, with an angled tab that gives a bit more leverage. Only complaint I have is the tab does look a bit less svelte than the tab design from Chad Nell or Enrique Pena.