Apparently the purpose of the chain is not to make the squat easier on the way down (though it does, in fact, have that effect), but rather to make it harder on the way up. It is supposed to train the kind of leg drive and explosiveness that are valuable for a position in which one must drive through people.
By the way, I promise this will not become a regular feature (I don't consider my lifts all that impressive), but I figured I might as well round out the complement of core lifts.
These videos were taken between 02.00 and 03.00 Germany time.