This is a fantastically informative thread -- and thanks for the great photos, Piper235b!
As I said in another post, I've never seen the recessed striker (firing pin) assembly in a Sako in the U.S. in forty-five years of looking, so their origin is quite a puzzle, as is the fact that they seem to be limited to Australia, at least so far as info on this thread has revealed.
One thing which is obvious about the recessed striker is that its mass would appear to be significantly less than that of the "regular" striker. This would mean several things: One, the firing pin fall (lock time) would be faster, assuming the same weight spring. Two, the firing pin striking force (momentum) would be lighter due to the lighter mass. Three, unless a significantly stronger spring were used, the striking force of the firing pin might be marginal for thick/hard primers, but the action's accuracy potential would be theoretically improved due to the faster lock time and less inertia imapacting the aim of the rifle when the striker is released. I wonder if anyone has observed any difference in ignition between the two types of firing pin assemblies?