interesting....I think the big change for GE's switch to the straight vanes, was to increase capacity, for at that time, was standard, and usually 8 to 12 pounds...
by using the straight vane, it eliminated the space taken up by the ramped activators funnel design....
and so before the 18lb unit came out, they could get away with 14 and 16lb rated capacities....
oddly enough though, the ramped activator of the V12 was very effective at turning over a heavy load....most likely why they returned to that design, just a bit more trimmer...