Yeah, which is why the data is backed up by multiple panel analyses that actually make the argument for causation. The US data shows that crime rates rose like clockwork approximately ~20 years after leaded gasoline is used en masse, and drops ~20 years after it was banned.
Did they also account for changes in how crime rates are reported over time?
One would have to account for hundreds of different variables before you could ever conclusively prove a connection between lead and crime.