Bsms go play with a single jointed bit. Any force on the ring pieces can make the bit fold up like a pair of tongs, even with your little diagram there.
If there was a rider, it would be folded even if the rein angle was 'parallel to the jaw'
Now play with a 3 jointed bit. It can never fold up as much as a single jointed bit.
That alone, makes it more mild. Not saying a reg. Snaffle is a harsh bit.
Horse preference is the most important though. If you horse prefers a single, use a single. If they like more joints, then go that option. If they want a myler, then go with a myler.
"Strength is the ability to use a muscle without tension"