One possible reason why that logic might not hold might e.g. simply be that restrictions on screen time might correlate with more involved parents.
There is causality when all the kid can draw involves violence with vague shapes, while others can draw complex sceneries.
Where I do agree is that at the end of the day, the screen is not really the issue, it's what you watch on it.
Without anything else all you have is correlation.
There is no logically sound basis for your argument.
It's staggering to me how many arguments in this thread are devoid of proper application of reasoning.