Exactly. I’m not sure I believe this, and definitely don’t have any evidence to back it up.
If kids are safer because they are staying at home, then we can’t criticise parents for not letting them out to play by themselves. That would be like saying Donald Trump doesn’t need bodyguards since very few presidents have been attacked.
More accidents happen at home than anywhere else, so perhaps kids are safer outside. As an example, my brother broke his arm in a pillow fight when he got knocked off the bed.