#2 is simply wrong. Children are corrected when their grammar is off so they do get to see incorrect sentence structure. It's questionable if children could learn language from only watching TV, but that's not the standard learning environment.

PS: I am far from the first person to point that out. At this point they are treating it as an axiom because they continue to believe it despite the disproof of their premises.

Yet, they consistently ignore this input. This has also been pointed out dozens and dozens of times.