The locking mechanism in both the Morgan and the Alwilda is different from the one in the Schrade.
Not all Schrade marlin spikes lock, the locking ones that I've seen are lockbacks with a lever that lifts up the backspring to unlock, this mechanism is common in American rigging knives and is found in those made to US government specifications.
The locking lever in the Morgan and Alwilda looks to me like what I'm used to see in British rigging knives, when the lever is rotated toward the blade a section of the lever inside the knife blocks the spike's spring preventing it from moving back and thus locking the spike.
So it seems to me that maybe the Japanese knives copy the general lines of the Schrade but with a British style lock.
I have seen another Japanese rigging knife, by Kershaw, following the style of the British Army Knife, with modern looking black plastic or FRN handles, it was obviously made as a user and it was a good one too.
Luis