The key and accurate part of that is this: “Two or three decades ago, children were roaming neighborhoods in mixed-age groups, playing pretty unsupervised or lightly supervised.” The rest is pretty dubious differences, but this is key because kids were misbehaving all the time then, too, they just had lots of opportunity to do it without adult supervision. Which made it easier to conform to restrictive rules when they were supervised, because the opportunity to act without constraints was usually right around the corner.