Personally I think the 2 snap method is overkill and actively detrimental as that removes any ability for your straps to swivel on the snap, which can cause all kinds of snags and bunching up of the strap when you're moving around.
I guess the matter isn't so bad due to the very tiny forces involved, but it flawed thinking. People add the second snap for extra strength when they could be using higher quality snaps and and double up the ends of elastics where the snap sit instead.