Post hoc, ergo propter hoc?

> But the article doesn't consider whether restricting children's wanderings is the REASON it is so much safer for children now.

The article considers exactly that.

> Similarly, in an international study that looked at 7 to 15 year old children across 16 different countries they found that most english-speaking countries were in the lowest autonomy tier (12th- Ireland, 13th- Australia, 16th- South Africa). Americans weren’t surveyed, but countries like Finland, Germany, Norway, Sweden, Japan, and Denmark scored the highest on autonomy.

These countries are considered because they would generally be considered roughly as safe as one another (generally safer than America). These countries are the counterexample to your hypothesis: you can simultaneously have safe and independent children.