I understand that this type of bike is becoming the standard for training newcomers to bike-riding (rather than "training wheels" which don't serve much purpose).

It's certainly becoming more popular for teaching kids to ride, although the models sold for that purpose are godawful expensive. When we were thinking about it for Hoss, a friend instructed me to just take the pedals off his bike. He figured out how to balance before I got around to it, though.