A friend of mine, PhD in early childhood education, told me the contrary: Toddlers instinctively know their limits and will not "bite more than they can chew", at least with gross motor skills.

My personal experience confirms this: for example, when teaching my young kid of 18mo to climb down stairs standing, I would stop holding his hands and observe his behavior. He would initially try to go down a step on his feet while holding the side rail, then hesitate and ask for my hand. If I told him to do it himself, he would instead sit down and slide down gently.

There could be permanent consequences either way. Children of overprotective parents tend to live less:

https://neurosciencenews.com/overprotective-parents-child-lo...

I don’t know. Our kid frequents these playgrounds and it’s interesting to see how the usage changes over time. The kid quite frequently signals when it thinks something is too high or a slide to steep or whatever. And most kids seem to be rather cautious.