Professor Mackett goes on to say: “Fears over road safety and ‘stranger danger’ need to be balanced against soaring levels of childhood obesity and poor health. Letting a child out to play is one of the best things a parent can do for their child’s physical health and personal development.

A delicate point. I don't think that 'too much freedom' is good either.

Of course it doesn't hold for any child, but if a certain degree of freedom (in a certain regard) leads to an increase in negative effects overall, and/or the negative effects exceed the possible positive effects overall, then I would call it 'too much freedom'.