thanks for the post.
i was hoping it would explain the reason for olde world 'cotter pins' (which hold the cranks to the bottom bracket axle). these were always a pain in the neck to remove and instal.
olde world
new world
the video doesnt discuss it, but i got a good explanation here
Bicycle Specialties: Aluminum and steel cranks.
if i got it right, the old world used steel axles and steel cranks. any cotterless technology was subject to high wear/wobbly. cotter pins were the best way of mating a steel axle to a steel crank.
in the new world, the steel axle is mated to an aluminum crank which fits much tighter and doesnt experience the same wear.