Mine didn’t have a brake on his balance bike and was shredding the gnar on it. He was going so fast I had to ride to keep up with him, and he was doing trails like the orange at Laggan and dirt jumps with a big run in slope.
Feet can stop you even if you are going fast downhill and they can help you corner, mine figured out that if he was going fast down a trail a little bit of right foot down would help him turn right etc :D
Not having brakes on a balance bike certainly didn’t hold him back – his first pedal bike was a back pedal brake, but he was using hand brakes before he was three. He is still only 3 and comes fast down steep trails using his front brake only must sort out that rear brake I suppose
That said, I have nothing against brakes on balance bikes either. And I can obviously see the advantages, but for me it wouldn’t be a deciding factor.