Hmm, based on my observation, I noticed the opposite to be true. Some of the earlier versions seemed to have had the butterfly clasp while the ones currently available have this one. Or, maybe they just mixed it up.
The Striking 10th Stratos also uses this clasp. However, on the 36,000 vph, it seems that they have consistently used the butterfly.
At one point, I had the bracelet with the butterfly clasp but I still prefer this one.
It does take a bit of getting used to, but I have no issues operating it with one hand.