I'm a believer in balance bikes. But I am more of a believer in appropriate sized bikes. If a bike is too big, so the child can "grow into it", imo, it only becomes a clumsy thing they can not control and can't learn to use, and the child only looses confidence and doesn't use it. This goes for balance bike and regular bike. A bike is not a pair of pants you can roll up, pull in the waist and make due with. Balance bike needs to be able to have feet firmly on the ground, and a rising seat so when they get taller you can move it up. Regular bike needs to be able to have feet almost firmly on ground when 1st learning (so they can hold one foot on ground while starting off with other foot on the pedal), when expert biker to have feet at least tip toe on ground.
However, I also understand that most people can not afford a small balance bike for their 2-3 yo, a regular bike for their 4-5 yo and then another bike for their 6-7 yo.... So, older siblings bikes, friends bikes, garage sale.... here we come.
DS went from 3 wheeler to bike. He used training wheels for about 3 months. It would have been much longer, but at the same time we got a used balance bike, so he was able to take off the training wheels rather quickly. Still it was a learning experience because he was over 5 and feeling like he might fall without the training wheels. They were a crutch, in other words. DD got his old balance bike, and a few months later she instantly transitioned to regular bike with no training wheels. No reason to introduce training wheels, since she already had her balance and pedal motion. It was a very smooth transition. She was a good bike rider by 3.5, and a pro at just over 4 yo, she can bike fast up/down hill, in snow and sleet....
So to answer the original question, I am a huge balance bike fan. However, I put more stock in appropriate bike size than in whether it is a true balance bike or a regular bike with pedals off. However, buying a bike with pedals off that is clearly too big for the child, in order to not have to get another bike later, imo won't work.