I think it's one of those situations where CRKT changed the blade steel as they were going along, without any announcement or anything.
Like they did with the Crawford Kasper, going from AUS 6M to 420J2 at some point and being very low key about it. And the M16 in some versions, going from AUS 8 to AUS 4.
In fact, 1sks.com says, in part, about the First Strike:
"
The blades are AUS 6M stainless steel in a satin finish. The blade shape is a combination of the ancient chokuto straight sword and the classic mohora-zukuri double edge tanto. The grind is what Steve calls a convex zero edge, or appleseed cross section, resulting in an edge that is much stronger than taper or hollow grinds. The massive blade thickness continues through the tapered full tang, resulting in incredible strength from tip to butt."
http://www.1sks.com/store/crkt-steve-corkum-small-first-strike.html